The Red Cross delivered aid to areas around the battered Baba Amr district of the Syrian city of Homs yesterday, but was blocked from entering the former rebel stronghold itself, three days after anti-government fighters fled a month-long siege.

In a further indication civilians are being caught up in the conflict, up to 2000 Syrians have fled into neighbouring Lebanon, the United Nations Refugee Agency said.

The International Committee of the Red Cross (ICRC) said it had been prevented from entering Baba Amr by Syrian Government forces despite receiving official permission. Activists said the move was to stop aid workers witnessing army massacres.

"We have the green light, we hope to enter, we hope today is the day," said the ICRC's Damascus-based spokesman Saleh Dabbakeh. "We are very concerned about the people in Baba Amr."

After a month of bombardment by President Bashar al Assad's forces, concerns mounted for freezing, hungry and wounded civilians in Homs, which on Saturday came under renewed shelling by Government troops, anti-Assad activists said.

UN Secretary-General Ban Ki-moon said on Friday he had had "grisly reports" that troops were executing and torturing people in Homs after insurgents left.

Aid workers began delivering supplies to areas near Baba Amr that people had fled to, the ICRC said. "It is a positive step. But we want to enter Baba Amr today," spokesman Hicham Hassan said.

South of Homs, the border town of Qusair came under fire from Government troops, forcing residents to flee on foot to neighbouring Lebanon, a witness said.

"People said they were sat at home and suddenly the shelling started and they fled. They said it was tank shelling and gunfire," said journalist Afif Diab.

At the border he had found the refugees were mainly women fleeing with their children. Blasts could be heard from the Lebanese border, seven miles from Qusair.

Other Lebanese border sources spoke of attacks in Syria by aircraft, but reports could not immediately be verified.

"Between 1000 and 2000 Syrians are in the process of coming from Syria to Lebanon," the UN Refugee Agency's deputy representative in Lebanon, Jean-Paul Cavalieri, reported.

Lebanon deployed more troops to its northern border in response to the violence in Syrian towns nearby in a sign that the conflict risks dragging in regional powers with rival sectarian interests.

Anti-Assad activists reported Government raids in Hama in which one young man was shot dead, and heavy shelling in the town of Rastan, north of Homs, where rebels have been hiding.

Clashes between Free Syrian Army defectors and Syrian troops were reported in Jebel al Zawiya in Syria's north, and activists said Government forces had used tear gas to disperse a protest in the northern city of Aleppo.

The UN says Syrian security forces have killed more than 7500 civilians since the revolt against the Assad family's four decades in power began a year ago.

The Syrian Government said in December "armed terrorists" had killed 2000 soldiers and police during the unrest.