The UN human rights chief has called for a full investigation of alleged abuses carried out by Syrian authorities against anti-government protesters.
Navi Pillay, the high commisioner for human rights, said on Wednesday that her office had received reliable reports that up to 10,000 people have been detained and more than 1,100 killed, most of them unarmed civilians.
Pillay told the Human Rights Council in Geneva that there were "numerous cases emerging of the torture and ill-treatment of detainees".
She said human rights campaigners, political activists and journalists had been particularly targeted among those detained.
"I remind the Syrian authorities that violations of international law are serious crimes for which perpetrators can be held accountable," she said.
Turkey's Prime Minister Recep Tayyip Erdogan met Syrian president Bashar al-Assad's envoy Hassan Turkmani for nearly three hours in Ankara on Wednesday in an apparent fresh effort to persuade Damascus to end its bloody crackdown.
Erdogan last week accused Syria of perpetrating an "atrocity" against demonstrators.
No statement was made after the Ankara talks.
The army assault on Jisr al-Shughur and other towns in Idlib province in northern Syria has sent at least 9,o00 people fleeing into Turkey.
Ahmet Davutoglu, the Turkish foreign minister, toured one of the refugee camps in the country's Hatay province on Wednesday, chatting with refugees.
"We are seeing a humanitarian situation here and developments are concerning," Davutoglu told
Earlier he had denied speculation that Turkey would stop accepting refugees once their numbers hit 10,000.
UN Secretary General Ban Ki-moon again called on Assad to implement reforms, in a speech Wednesday.
He urged the Syrian authorities to "protect their people, respect their rights, listen to their voices ... create the conditions for refugees to return, implement reforms now before it is too late".
The UN has a team of investigators interviewing refugees who have fled across the border to Turkey but the world body has not been allowed to send a fact-finding mission into Syria.
In the conservative Damascus suburb of Harasta, security forces fired live ammunition on Wednesday to disperse a night protest by 200 women demanding the release of their husbands and relatives, arrested in an intensifying security sweep to put down the three-month uprising, a witness said.
"They carried placards saying 'where is my husband' and where is my brother' and pictures of the prisoners. No one was hurt but it was barely 10 minutes into the demonstration when they opened fire," the witness said.
Military operation 'imminent'
In the north, residents of Maarat al-Numan fled their homes on Wednesday as the military announced it was preparing for an operation in the town.
Tanks surrounded the town and Major-General Riad Haddad, head of the military's political department, said said "gunmen" inside were "intimidating people into fleeing the area".
Haddad said the government feared a repeat of the violence in nearby Jisr al-Shughur, where authorities claimed gunmen killed 120 officers and security personnel last week, prompting troops to storm the town.
Activists said the security forces were shot by government troops, after they refused to open fire on civilians.
As foreign media have been banned from Syria, accounts of the recent events in Jisr al-Shughur cannot be verified.
The official news agency said the army had found a second mass grave in the town containing the bodies of soldiers and police killed by "armed terrorist groups".
Activists and witnesses say dozens of civilians have been killed in Jisr al-Shughur and that there were clashes between defected soldiers and security forces.
According to a toll released on Tuesday by the Syrian Observatory for Human Rights, the violence in Syria has claimed the lives of 1,297 civilians and 340 security force members in Syria since the unrest erupted mid-March.