Russia has again blocked a United Nations Security Council resolution condemning Syrian airstrikes on rebels and civilians.
Wednesday's British-sponsored draft expressed outrage at the missiles and barrel bombs dropped on the besieged city of Aleppo since last month. The attacks have killed at least 700 people and wounded thousands.
Diplomats say Russia wanted to add amendments to the resolution which they say would have made it meaningless.
Russia - a strong Syrian ally - and China have blocked other resolutions condemning the Syrian government. But Russia backed moves that forced Syria to give up its chemical weapons. It is also co-sponsoring with the United States this month's peace talks in Geneva.
Earlier Wednesday, Syrian activists say rebels in Aleppo seized control of a hospital that had been used as a base by their al-Qaida-linked rivals.
The Syrian Observatory for Human Rights said a loose coalition of moderate and Islamist rebel groups took control of the base after a series of strikes against the Islamic State of Iraq and the Levant (the ISIL).
Fighting among groups of secularist rebels, moderate Islamists, and extremists - all of whom want to get rid of President Bashar al-Assad - has been raging for a week.
ISIL's spokesman Abu Mohammed al-Adnani had issued a defiant message late Tuesday urging his forces to crush the rival rebels. He also warned that ISIL had declared war against the mainstream opposition Syrian National Coalition and the military command of the Western-backed Free Syrian Army.
Al-Qaida's official affiliate in Syria, the al-Nusra Front, is calling for a truce among rebel factions, saying the infighting only benefits Assad's government.