Moscow's UN envoy, Vitaly Churkin, told reporters the resolution was one-sided and supported the armed opposition.

Western nations praised the resolution, which passed by 133 votes to 12 with 31 abstentions.

It criticizes both the UN's own Security Council and the government of Syrian President Bashar al-Assad.

The assembly debated the resolution, which was proposed by Saudi Arabia, shortly after the resignation of UN-Arab League envoy Kofi Annan and the failure of his six-point peace plan.

In Syria, government forces backed by tanks launched a new assault in Damascus while shelling continued in the country's largest city, Aleppo.

Activists say more than 20,000 people - mostly civilians - have died in 17 months of unrest.