The Syrian president has told Kofi Annan, the UN and Arab League envoy, that no political solution is possible in Syria while "terrorist" groups are destabilising the country.

Annan, who is set to meet Bashar al-Assad in Damascus for a second day of talks on Sunday, offered no immediate comment after the meeting, aimed at halting bloodshed that has cost thousands of lives since a popular uprising erupted a year ago.

"Syria is ready to make a success of any honest effort to find a solution for the events it is witnessing," state news agency SANA quoted Assad as telling Annan during two hours of talks on Saturday.

"No political dialogue or political activity can succeed while there are armed terrorist groups operating and spreading chaos and instability."

Annan, a former UN secretary-general, is due to meet Syrian dissidents before leaving Damascus on Sunday.

Annan has called for a political solution, but the opposition says the time for dialogue is long gone.

Assault on Idlib

While Assad and Annan discussed the crisis, Syrian government forces were stepping up attacks on the northern city of Idlib, an opposition bastion, for a third straight day, in their latest onslaught on opposition fighters and civilians.

The troops attacked Idlib for hours with dozens of tank shells as the forces moved to encircle the town, an Associated Press news agency team in Idlib reported.

Syrian forces had been building up for days around Idlib, the capital of a hilly, agricultural province along the Syria-Turkey border that has been a centre of anti-government protests.