Syrian activists say clashes between rebels and government forces in the capital, Damascus, have continued for a third day, in what has been the heaviest period of fighting in the city since the revolt against President Bashar al-Assad began.

Amateur video posted online Tuesday appeared to show panicked Damascus residents fleeing the fighting earlier this week. The video has not been independently verified.

The fighting comes as the U.N. Security Council debates two competing resolutions on Syria.

Britain, France, Germany and the United States are pushing for a 45-day renewal of the U.N. observer mission in Syria along with a threat of sanctions against the Assad government. Russia's proposal calls for a longer extension of the mission, but no sanctions.

U.N. Secretary-General Ban Ki-moon is visiting China, while U.N. envoy Kofi Annan holds talks with Russian President Vladimir Putin in Moscow.

Russia and China have vetoed previous Security Council resolutions calling for tough action against Syria.