Syria protests: US and UN condemn armed crackdown
There has been international condemnation of the Syrian government following reports that troops fired on peaceful demonstrators on Friday.
The US said Syria was trying to "repress and intimidate demonstrators", while UN chief Ban Ki-moon urged Damascus to exercise restraint.
Witnesses said dozens of people had been killed during the protests - this cannot be independently confirmed.
The rallies came a day after Syria said it would consider political changes.
Protests were staged in towns and cities across Syria, including the capital Damascus.
In the US, White House spokesman Jay Carney said Washington was deeply concerned at what was happening in Syria.
"We strongly condemn the Syrian government's attempts to repress and intimidate demonstrators," Mr Carney said late on Friday.
Meanwhile, UN Secretary General Ban Ki-moon telephoned Syrian President Bashar al-Assad to urge "maximum restraint".
Mr Ban also stressed that Damascus had an obligation to respect the fundamental rights of its citizens.
Amnesty International - which expressed fears that 55 people have died in Syria in the past week - also condemned the treatment of demonstrators by Damascus.
'God, Syria, Freedom'
Gunfire was heard in the city of Deraa, which has become the centre of a serious challenge to the regime of President Assad. The marchers who took to the streets in Deraa had attended funerals for some of the 25 protesters killed on Wednesday.
Some of the protesters started a fire under a bronze statue of Mr Assad's father, the late President Hafez al-Assad, witnesses reported.
Another group of protesters trying to reach Deraa were killed in the nearby village of Salamen when security forces opened fire.
A government official confirmed that at least 10 protesters had died, although witnesses said up to 20 people had been killed.
In Damascus, around 1,000 were reportedly continuing a protest into Friday night, vowing to stay until their demands had been met.
Earlier, hundreds marched on King Faisal Street chanting: "Peaceful, Peaceful, God, Syria, Freedom." This protest was broken up by security forces and many were arrested, reports say.
Another protest reported to the BBC by an eyewitness took place around al-Rifai near Qasar Sousah Square.
Supporters of Mr Assad were also staging large protests in the capital, and clashes erupted between the two sides.
In the central city of Hama, hundreds of people were said to have gathered on the city streets to chant "freedom".
In 1982, the Syrian army put down an uprising led by the Muslim Brotherhood in Hama. Rights groups believe that tens of thousands of civilians were killed when large parts of the city were destroyed in the military assault.
In Tall, witnesses quoted by the Reuters news agency said about 1,000 people had rallied to show their support for the Deraa protesters, and were chanting slogans denouncing members of the ruling Assad family.
Demonstrations which ended in violence were also reported in the cities of Latakia and Homs. One person was killed in each place, the Associated Press news agency quoted an activist as saying.
On Thursday, Damascus said it would consider political reforms, including the possible ending of emergency laws introduced in 1963.
The government also said it would put on trial those suspected of killing several protesters in Deraa.