DAMASCUS (AFP) - Tanks swooped on another northern town Thursday as Syria's army pressed its crackdown on dissent and the United States condemned the "outrageous use of violence" to quell a popular uprising. The European Union on Thursday began work to toughen sanctions against Syria, looking at adding firms and a dozen people to a blacklist which already includes President Bashar al-Assad and key allies. Several diplomatic sources said experts from the 27-nation bloc were discussing ways Thursday of "widening sanctions" against Damascus. "The idea is to move up a level," said a diplomat who asked not to be identified. "Talks are focusing on new names and entities." Meanwhile, the United States is stepping up contacts with Syrians inside and outside the country who are seeking political change, the State Department said Thursday. UN chief Ban Ki-moon on Thursday urged Syrian President Bashar al-Assads regime to stop killing people, as pressure mounted on Damascus over its widening crackdown in the north. "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 also said the military had cut the Aleppo-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." Pro-democracy activists, meanwhile, called for new Friday protests against the ruling Baath party. The Khan Sheikhun deployment marks a continuation of military operations in the northern province of Idlib, where forces have targeted Ariha, Maaret al-Nooman, Jisr al-Shughur and its surroundings, an activist said. A leading Turkish daily reported on Thursday that Turkish forces may enter Syria to create a military buffer zone if the unrest there degenerates. Commenting on his article in Posta, prominent journalist Mehmet Ali Birand told AFP 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 said. This option was raised at the highest level, some time ago." Turkish Foreign Minister Ahmet Davutoglu, who did not confirm the report, said Ankara would supply humanitarian aid to thousands of Syrian refugees. "There are at present more than 10,000 people just over our border, on the other side of the barbed wire," he told journalists. "We have decided to help our Syrian brothers to meet their urgent needs for food," Davutoglu said a day after visiting refugee camps set up by the Red Crescent in Hatay province, adding that the Syrian authorities had been informed. Turkish Prime Minister Recep Tayyip Erdogan met President Bashar al-Assad's envoy Hassan Turkmani for nearly three hours on Wednesday in an apparent fresh effort to persuade Damascus to change course. No statement was made afterwards. 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. Washington urged an immediate end to the crackdown. "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. The European Union began work on Thursday to toughen sanctions against Syria, looking at adding firms and individuals to a list of Assad allies already hit by sanctions. "The idea is to move up a level," said a diplomat in Brussels who asked not to be identified. "Talks are focusing on new names and entities." The EU to date has slapped two sets of sanctions against Assad's regime, with EU foreign ministers late May adding Assad to a blacklist of 23 Syrian officials hit by an assets freeze and travel ban. Several European nations - notably Britain, France, Germany and Portugal - have joined Washington in pushing for a UN resolution condemning the crackdown, but this is opposed by permanent Security Council members China and Russia. "Outside forces should not interfere in internal processes in the countries of the region," Presidents Dmitry Medvedev and Hu Jintao said in a joint statement on the unrest in the Arab world. 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 (30 miles) from the capital. Abdel Rahman said thousands of people also protested in Hama, 210 kilometres (130 miles) from Damascus, and elsewhere.