Syrian activists say all communications are down in large parts of the countryside and in the flashpoint city of Aleppo, where government forces reportedly have been pushing rebel forces out of position since last week.

It is unclear what caused the cut in communications since early Sunday. But despite this, the London-based Syrian Observatory for Human Rights said it had reports that the army was continuing to shell rebel-held districts in the country's largest city. There also were reports of violence elsewhere in the country.

The Arab League has postponed a meeting of foreign ministers that had been scheduled for Sunday in Jeddah, Saudi Arabia, to discuss the Syrian situation and a replacement for peace envoy Kofi Annan, who resigned earlier this month.

An Arab League official did not give a reason for the delay and did not say when the meeting might be rescheduled.

The announcement came while U.S. Secretary of State Hillary Clinton is in Istanbul to discuss Syria with Turkish leaders.

Officials say Clinton is meeting with President Abdullah Gul, Prime Minister Recep Tayyip Erdogan and other Turkish officials to discuss how to deal with neighboring Syria. Turkey is hosting tens of thousands of Syrians who have fled the violence in their home country.