A ceasefire in the Syrian city of Homs has collapsed with reports of Syrian forces pounding central districts in the city.
Those opposed to the Government of President Bashar al-Assad have also attacked a police station in the northern province of Aleppo.
This comes as the United Nations prepares to deploy a team of monitors to oversee the ceasefire.
Russia and China joined the rest of the United Nations Security Council to authorise the deployment of up to 30 unarmed observers to Syria.
It is the first resolution the 15-nation council has approved since the anti-government uprising began 13 months ago.
Moscow and Beijing have twice vetoed previous council resolutions on Syria.
Before agreeing to support what was originally a US-drafted text, Russia had demanded that the US and European delegations dilute it so that it would not "demand" that Syria comply with the resolution.
The approved resolution uses softer language so that it "calls upon" Syria to implement it.
It also calls on all parties, including the opposition, "immediately to cease all armed violence in all its forms."
US ambassador to the UN Susan Rice said the resolution emphasises the necessity for the Syrian Government to immediately withdraw all troops and heavy weapons from population centres.