Lebanon clashes: Fresh clashes breach truce in Tripoli
Fresh clashes have erupted in the Lebanese city of Tripoli, breaching a truce agreed by local leaders on Wednesday.
At least one person was killed as supporters and opponents of Syria's President Bashar al-Assad fought for a fourth day.
The fighting between the Sunni and Alawite neighbourhoods has already killed more than 12 people this week.
Tanks have been deployed to try to calm the situation.
The UN political chief Jeffrey Feltman described the situation as "precarious".
He told the UN Security Council that, as the situation in Syria deteriorated, there was a risk that it could escalate in Lebanon too.
"The need for continued international support to the government and the Lebanese Armed Forces [has become] increasingly important," he said.
He added that UN Secretary General Ban Ki-moon was concerned about two-way arms smuggling across the border between the two countries, in violation of a UN resolution.
In an unusually strongly worded statement, Lebanese President Michel Suleiman appeared to suggest that Lebanon would not always remain in Syria's shadow.
"When any relationship with a foreign entity harms Lebanon, we end it. And when the relationship is again in Lebanon's interest, we reinstate it," he said, in comments published in Lebanese media.
The fighting on the streets of Tripoli, Lebanon's second-largest city, was centred around the Sunni Muslim district of Bab al-Tabbana and the Alawite district of Jabal Muhsin.
The city of nearly 200,000 people is one of the country's most volatile sectarian faultlines, with a small Alawite community living in the midst of a Sunni majority.
On Wednesday, the army tried to stop the violence but was forced to retreat after sustaining casualties. It said it would enter into dialogue with leaders of the two communities in order to prevent the entire country being dragged into a state of unrest.
Prime Minister Najib Mikati has appealed to both sides to end the "absurd battle" and, speaking of the conflict in neighbouring Syria, warned against being "drawn into this blaze around Lebanon".
Syria's President Bashar al-Assad is an Alawite and members of the heterodox Shia sect occupy key positions in the government and security forces.
Syria's majority Sunni community has been at the forefront of the revolt against the state and has borne the brunt of the crackdown during the conflict, which the UN says has left more than 18,000 people dead.
The BBC's Barbara Plett, in Tripoli, says violence has flared several times in Tripoli, including in early June when 15 people were killed, but locals say the last two days of clashes were particularly intense. One witness said heavier weapons were being used, and over a larger area than normal.
Our correspondent says government policy has been to try to disassociate the country from the Syrian crisis, amid concern that it might reignite the divisions that fuelled Lebanon's own 15-year civil war.
But the more sectarian the violence becomes in Syria, the harder it is to prevent it from seeping across the border, she adds.
Syria was the dominant foreign power in Lebanon for some 30 years and attitudes to the conflict which erupted there last year colour Lebanese politics beyond Tripoli.
Last week, a Lebanese Shia Muslim clan kidnapped dozens of Sunnis in retaliation for the abduction of a Lebanese Shia man by rebels in Syria.
The rebels had accused the man, Hassan Mekdad, of being a member of the powerful Shia Islamist movement Hezbollah, who had entered the country to fight for the government. However, Hezbollah has denied any connection with the clan member or the kidnappings.