Media playback is unsupported on your device Media caption The war in Syria could be about to enter its final stage 
 
 Russian President Vladimir Putin has rejected Turkey's calls for a truce to prevent a "bloodbath" in north Syria. 
 
 At a trilateral meeting with Iran and Turkey, Mr Putin said Russia would continue its fight against "terrorists" in Idlib province. 
 
 Idlib is the Syrian opposition's last major stronghold, with almost three million residents. 
 
 Syrian military forces, backed by Russia and Iran, are poised to launch a major offensive there soon. 
 
 The three-way meeting in Tehran had been seen by many as a final chance to prevent a large-scale battle in Idlib. 
 
 Syria has been in a civil war since 2011, after a peaceful uprising against President Bashar al-Assad turned into a conflict that has killed more than 350,000 people. 
 
 Why are these countries involved? 
 
 Iran, Russia and Turkey have played central roles in the Syrian conflict. 
 
 Turkey - which has long backed some rebel groups - fears an all-out assault will trigger another major refugee crisis on its southern border. 
 
 Turkish President Recep Tayyip Erdogan told his Russian and Iranian counterparts: "We don't want Idlib to turn into a bloodbath." 
 
 "Any attack on Idlib would result in a catastrophe. Any fight against terrorists requires methods based on time and patience." 
 
 Image copyright Reuters Image caption Improvised gas masks are being tried out in Idlib ahead of the expected offensive 
 
 However, Russia and Iran are allied to Syria's President Assad, and say jihadist groups in Idlib must be wiped out. 
 
 Russian air strikes, and thousands of fighters backed by Iran, have helped the Syrian military attack rebel areas. 
 
 At Friday's meeting, Iran's President Hassan Rouhani argued that "fighting terrorism in Idlib is an unavoidable part of the mission of restoring peace and stability to Syria". 
 
 Meanwhile Mr Putin said "the legitimate Syrian government has a right and must eventually take control of its entire national territory". 
 
 Why is Idlib so important? 
 
 The province is the last major stronghold of the rebel and jihadist groups which have been trying to overthrow Mr Assad for the past seven years. 
 
 Image copyright AFP Image caption The population of Idlib has been swollen by refugees from other parts of Syria 
 
 It straddles major highways across Syria - and if it is retaken by the government, would leave the rebels with just a few isolated pockets of territory across the country. 
 
 The province is not controlled by a single group, but rather by a number of rival factions, including a jihadist alliance linked to al-Qaeda, and a rival National Liberation Front which is backed by Turkey. 
 
 Up to 30,000 rebel and jihadist fighters are believed to be in Idlib. 
 
 But the vast majority of Idlib's residents are civilians. The UN says the region is home to some 2.9 million people, including a million children. 
 
 More than half of the civilians have already been displaced at least once from elsewhere in Syria and have nowhere left to go. 
 
 Why is concern growing? 
 
 The UN fears a large-scale offensive in Idlib will lead to a humanitarian disaster. 
 
 Without a political solution in Syria, "we will see this war reach new levels of horrors", the UN special envoy on Syria, Staffan de Mistura, said. 
 
 Meanwhile, the new US envoy for Syria, Jim Jeffrey, said the anticipated conflict would be a "reckless escalation", and that "there is lots of evidence that chemical weapons are being prepared." 
 
 Image copyright AFP Image caption Protesters in Idlib demonstrated against the Syrian government and Russia on Friday 
 
 He did not give details of the evidence he was referring to. 
 
 Mr Jeffrey said a "major diplomatic initiative" was now needed, and there was "a new commitment" by President Donald Trump to remain involved in Syria until the Islamic State group (IS) was defeated and Iranian fighters left the country. 
 
 Mr Jeffrey said President Assad had "no future as a ruler" in Syria, but it was not Washington's job to oust him. He said the US would work with Russia on a political transition. 
 
 What do we know of chemical weapons use? 
 
 The Syrian government has denied ever using chemical weapons. 
 
 However, experts from the UN and the Organisation for the Prohibition of Chemical Weapons (OPCW) have said government forces were behind an attack involving the nerve agent Sarin on a rebel-held town in southern Idlib in April 2017 that killed more than 80 people. 
 
 The US state department warned on Monday that Washington would respond to any new chemical attacks by the Syrian government or its allies. 

 This image courtesy of Mustafa Alabdullah, an activist and resident of Idlib, shows protesters chanting as they holding Syrian revolution flags, in Harim, a town in Idlib province, Syria, Friday, Sept... (Associated Press) 
 
 This image courtesy of Mustafa Alabdullah, an activist and resident of Idlib, shows protesters chanting as they holding Syrian revolution flags, in Harim, a town in Idlib province, Syria, Friday, Sept 7, 2018. The rallies were a day of protests against Syrian President Bashar Assad and his troops' imminent... (Associated Press) 
 
 BEIRUT (AP) — Syrian government and Russian warplanes on Saturday targeted the southern edge of Idlib province with an intense wave of airstrikes and shelling, activists and a war monitoring group said, ratcheting up the military pressure on the densely populated rebel-held bastion. 
 
 The intense air raids came a day after Iran and Russia backed a military campaign in the rebel-held area despite Turkey's pleas for a cease-fire. Turkey has troops and 12 observations points that ring Idlib. 
 
 State-run Al-Ikhbariya TV said the government was retaliating against overnight shelling from rebel-held areas on a government-held town in Hama province, south of Idlib. The shelling late Friday in Mhradah killed nine civilians, according to state media. 
 
 But the government and Russian raids targeted a wide swath of rebel-held area in the southern edge of the rebel-held enclave that includes most of Idlib province and northern Hama province. 
 
 The Britain-based Syrian Observatory for Human Rights reported more than 30 air raids Saturday on a number of towns and villages in southwestern Idlib and Hama province. The area, which has been targeted over the last few days, overlooks government-controlled areas. 
 
 The intense raids forced schools to close in Khan Sheikhoun, an area under attack, according to the Observatory. 
 
 The local council of Morek, a town that serves as a crossing between Hama and Idlib, sent an urgent appeal, asking Turkey for a quick solution. "We need a quick solution or our town will burn!" the official pleaded in an audio recording shared on social media groups. 
 
 Separately, clashes broke out in eastern Syria in Qamishli, a town close to the border with Turkey, between government and Kurdish security members. The Observatory said the clashes left 10 government security personnel and seven Kurdish fighters dead. 
 
 The town is run by Kurdish-led administrators and forces, but Syrian government troops hold pockets of territory there, including the airport. Clashes rarely erupt there over turf control and authority, and are usually a reflection of deepening political tension between the uneasy partners. 
 
 Kurdish security forces, known as Asayish, said in a statement that a government patrol entered the areas controlled by the Kurdish militia in Qamishli and began arresting civilians, then shot at a Kurdish checkpoint sparking the gun battle. The Asayish said seven of its members and 11 government personnel were killed. 
 
 A journalist and resident of the area, Arin Sheikmos, said the government security troops went on an arrest campaign in Kurdish-controlled areas, detaining people it accuses of skipping compulsory military service. This prompted the clashes, which lasted no more than 20 minutes, Sheikmos said. 
 
 There was no immediate word about the clashes from the government. 
 
 The U.S-backed Kurdish administration has recently begun talking with the Syrian government — essentially seeking government recognition of its self-rule areas. But in recent days, the Damascus government announced it is holding local administration elections, including in Kurdish-ruled areas, undermining the negotiations and talk of Kurdish self-rule. 
 
 The Kurdish-led administration control nearly 30 percent of Syria, mostly in the northeastern part of the country, including some of Syria's largest oil fields. They seized the territories, with the backing of the U.S-led coalition, after chasing out Islamic State militants.
– Syrian government and Russian warplanes on Saturday targeted the southern edge of Idlib province with an intense wave of airstrikes and shelling, activists and a war monitoring group said, ratcheting up the military pressure on the densely populated rebel-held bastion. The intense air raids came a day after Iran and Russia backed a military campaign in the rebel-held area despite Turkey's pleas for a cease-fire, per the AP. Turkey has troops and 12 observations points that ring Idlib, which the BBC notes is the Syrian opposition's last big stronghold. The raids also come after President Trump warned Syria, Russia and their ally Iran they'd be making a "grave mistake" by attacking Idlib. The Britain-based Syrian Observatory for Human Rights reported more than 30 air raids Saturday on a number of towns and villages in southwestern Idlib and Hama province. The area, which has been targeted over the last few days, overlooks government-controlled areas. The intense raids forced schools to close in Khan Sheikhoun, an area under attack, according to the Observatory. The local council of Morek, a town that serves as a crossing between Hama and Idlib, sent an urgent appeal, asking Turkey for a quick solution. "We need a quick solution or our town will burn!" the official pleaded in an audio recording shared on social media groups.