The violence in Syria has killed 1,297 civilians and 340 security personnel since mid-March Damascus - AFP Tanks Thursday swooped on another northern town as Syria\'s army pressed its crackdown on dissent and the United States condemned the \"outrageous use of violence\" to quell a popular uprising. \"Dozens of tanks, armoured  cars, personnel carriers and army trucks have been deployed at entrance points to Khan Sheikhun, and soldiers have started going in\" to the northwest town near Hama, said rights activist Rami Abdel Rahman.
The head of the London-based Syrian Observatory for Human Rights, reached by telephone, also said the military had cut the Aleppo to Damascus road with barricades.
Another activist, speaking to AFP on condition of anonymity, said that on June 5, \"two tanks of the Syrian army were burned by the residents of Khan Sheikhun.\"
A leading Turkish newspaper reported on Thursday that Turkish forces may enter Syrian territory to create a military buffer zone if the unrest there degenerates into civil war and sparks a refugee crisis.
Commenting on an article he wrote in the daily Posta newspaper, prominent journalist Mehmet Ali Birand said a civil war in Syria could force up to 200,000 thousand people to flee towards Turkey.
\"The UN would become involved, and Turkey would be obligated to close its border and create a buffer zone,\" with its army, he told AFP.
\"This option was raised at the highest level, some time ago.\"
Turkish Prime Minister Recep Tayyip Erdogan met Assad envoy Hassan Turkmani for nearly three hours on Wednesday in an apparent fresh effort to persuade Damascus to change course.
No statement was made after the Ankara talks.
Last week Erdogan accused Syria of perpetrating an \"atrocity\" against demonstrators.
Washington urged an immediate end to President Bashar al-Assad\'s crackdown on pro-democracy protest that has swept through Syria since mid-March.
\"The international community has been shocked by the horrific reports of torture and arbitrary arrests, and widespread use of violence against peaceful protesters,\" State Department spokeswoman Victoria Nuland said.
Her statement was issued a day after the United States joined 53 other countries at the UN Human Rights Council in piling pressure on Damascus to allow its investigators in to examine the situation in Syria.
\"The United States condemns in the strongest possible terms the use of force by the Syrian government against peaceful demonstrators. This outrageous use of violence to quell protests must come to an end now,\" said Nuland.
Anti-regime protests were meanwhile reported overnight in the Mezze district of Damascus and at Harasta, Jisrin and Saqba on its outskirts, as well as at Zabadani some 50 kilometres from the capital.
Abdel Rahman said thousands of people also protested in Hama, 210 kilometres (130 miles) from Damascus, and elsewhere.
Near the flashpoint northern town of Jisr al-Shughur, officials on Wednesday showed journalists a grave containing at least five corpses they said were security forces.
Bulldozers also surrounded what state television identified as \"a new mass grave,\" found after the army took control of the town on Sunday.
The official SANA news agency has reported that armed groups had mutilated the corpses of members of security forces in Jisr al-Shughur.
Human rights activists have said the bloodshed in Jisr al-Shughur erupted during a mutiny by soldiers who refused to fire on the town\'s residents.
But government officials introduced journalists to a man who identified himself as a \"gunman who participated in a massacre at police headquarters\" on June 6. He said \"armed men\" had killed the victims.
The assault on Jisr al-Shughur and other towns and villages in Idlib province has sent thousands of people fleeing into Turkey.
By Wednesday, 8,421 Syrians had crossed the border. Most are staying in tent villages set up by the Turkish Red Crescent in Hatay province.
Protesters have described the army operation in the northern mountains as a scorched-earth campaign, and Syrian soldiers who deserted to Turkey have alleged they were forced to commit atrocities there.
The Syrian Observatory for Human Rights on Tuesday said the violence has claimed the lives of 1,297 civilians and 340 security force members since it began in mid-March.
Observers say the crackdown is being spearheaded by Assad\'s brother Maher, who heads the elite Fourth Division.
\"Judging by reports from the field, Maher al-Assad is everywhere at once, directing repression singlehandedly,\" said one Damascus-based analyst, who did not wish to be identified.
\"This reflects, I think, a perception that the ruling family is fighting for its life, and willing to crush society if that is what it takes,\" he told AFP.
Turkish officials said Hollywood superstar Angelina Jolie, a goodwill ambassador for the United Nations refugees agency (UNHCR), will tour refugee camps in the south on Friday.