The United Nations Security Council has demanded that Syria allow U.N. humanitarian chief Valerie Amos access to the country, while deploring continuing violence by the regime of President Bashar al-Assad.

Even Russia and China, which have vetoed two previous council resolutions against Assad, endorsed the U.N. plea for Amos to enter Syria.

The call comes as the rebel Free Syria Army was forced out of its stronghold in the city of Homs, a major setback for the beleaguered opposition.

Syrian rebels were forced to withdraw from the Baba Amro district of Homs on Thursday after government troops launched a widespread ground assault, ending a bloody 26-day siege of the city.

Homs-based activist Abu Imad told Reuters that both sides had suffered heavy casualties in the fighting, but with snow blanketing the area an accurate tally of the killed and wounded was impossible.

U.N. estimates put the number of civilians killed by government forces at 7,500, while activists say the death toll is closer to 8,000.

The Security Council statement cited the growing number of affected civilians, the lack of safe access to adequate medical services, and food shortages, particularly in areas affected by fighting and violence such as Homs, Hama, Deraa, Idlib, according to the Associated Press.

It called on Syrian authorities to allow immediate, full and unimpeded access of humanitarian personnel to all populations in need of assistance, in accordance with international law and guiding principles of humanitarian assistance.

On Wednesday, Amos, the U.N. undersecretary general for humanitarian affairs, expressed dismay that the Syrians had repeatedly denied her access to the country.

U.N. spokesman Martin Nesirky told the AP that Amos remained extremely flexible ... and she's still ready to go at a moment's notice.