"Army divisions entered Jisr al-Shughur and purged the state hospital of armed groups," a state television report said on Sunday. "Violent clashes pitched the army divisions against armed groups positioned inside and around the town," it added.

Jisr al-Shughur, in northwestern Syria near the border with Turkey, has been the focus of military operations for days, following what the authorities said was the massacre of 120 policemen by "armed gangs" in the town on Monday.

Human rights activists and residents deny the allegations of a massacre and say a number of policemen were executed by other security force members when they refused to fire on protesters in Jisr al-Shughur.

Harrowing reports of atrocities committed during Syria's crackdown, including deserting soldiers' accounts of massacred civilians, have sparked fresh international outrage.

UN chief Ban Ki-moon expressed concern at the mounting death toll, while the United States and the EU urged President Bashar al-Assad to let aid workers in to help relieve the humanitarian crisis.

As the death toll mounted, detailed accounts emerged from some of the thousands who fled to Turkey from the bloodshed in Jisr al-Shughur.

Among them were Syrian army deserters who told of atrocities committed by soldiers in suppressing protests, who themselves were under the threat of execution if they disobeyed orders.

Tahal al-Lush described the operation, in Ar-Rastan, a town of 50,000 people in Homs province, that had pushed him to desert.

"We were told that people were armed there. But when we arrived, we saw that they were ordinary civilians. We were ordered to shoot them," said Lush, with a blank stare in his eyes.

"When we entered the houses, we opened fire on everyone, the young, the old... Women were raped in front of their husbands and children," he said. He showed his military passbook and other papers as proof of identity.

A second conscript, Mohammed Mirwan Khalaf, said he had been in a unit stationed at Idlib, near the border. "Just in front of me, a professional soldier pulled out his knife and stabbed a civilian in the head, for no reason," he said.

In the Turkish city of Antakya, Nabil, one of the last Syrian aid workers out of Jisr al-Shughur, recalled the roar of helicopters and a "skull split in two" before he collapsed with a bullet in his back.

From his hospital bed, the Red Crescent employee recounted his last sights of the town last weekend, where Damascus said 120 police and troops had been massacred during anti-regime protests.

"The wounded, yes, I've seen hundreds. And dozens of deaths, maybe a hundred," the 29-year-old said. He had also seen victims of torture, he added. The turmoil has pushed 4,600 Syrians to seek refuge across the border in Turkey, a government official in Ankara told AFP.

"I am deeply concerned and saddened that so many people have been killed," Ban Ki-moon said during a visit to Colombia. He had spoken with Assad several times to express his concern, he said.

On Friday, UN officials said Assad was refusing to take telephone calls from Ban, as the UN Security Council discussed a resolution drawn up to condemn his crackdown.

Washington on Saturday called on Syria to let medics in, after reports that Syrian forces backed by helicopters had the previous day killed at least 25 protesters across the country, including in and around Jisr al-Shughur.

Fridays have become a rallying point in the revolt against Assad's regime, whose backlash on pro-democracy protests that erupted in mid-March has killed more than 1,200 civilians, rights groups say.

"The Syrian government’s offensive in northern Syria has created a humanitarian crisis," the White House said in a statement.

"The United States calls upon the Syrian government to stop this violence, and to give the International Committee for the Red Cross (ICRC) immediate, unfettered access to this region," it added.

The European Union also appealed to Assad to let international aid agencies in to help civilians caught up in the violence.

"I deplore the escalating use of brutal force against protestors in Syria in recent days," EU foreign policy chief Catherine Ashton said in a statement Saturday.

Both the EU and the US are backing a UN Security Council resolution proposed by Britain and France that condemns Syria for its crackdown.

But Russia and China, both veto-wielding members of the council, oppose any resolution on Syria.