Dubai Syrian troops appeared to be starting a ground operation to retake Baba Amr, the central city of Homs, where three Western journalists are among 100,000 residents trapped by a government assault that has raged for weeks.
A Syrian official vowed Baba Amr would be "cleaned" within hours while activists said: "Pray for the Free Syrian Army. Do not be miserly in your prayers for them."
The activists said regime forces discovered a nearly 2.5km-long tunnel that was used by activists to smuggle people, food and medicine into Baba Amr.
Meanwhile, UN humanitarian chief Valerie Amos said yesterday she was "deeply disappointed" that Syria has refused to allow her to the visit the country, where she had hoped to assess the need for emergency relief in besieged towns.
Kofi Annan, the United Nations-Arab League envoy for Syria, said he would hold talks in New York with UN Secretary-General Ban Ki-moon and member states on Syria.
In Kuwait, MPs overwhelmingly approved a resolution calling on the government to recognise the Syrian National Council as the legitimate representative of the Syrian people.