DAMASCUS: China and Russia vetoed on Thursday a UN resolution that could have imposed sanctions on the Syrian government angering the West as hundreds fled an army offensive against rebel districts of Damascus.

The head of the UN observer mission, Major General Robert Mood, warned that the violence was spiralling, as a human rights watchdog reported that the army was using tanks in its operations against rebel fighters in the Syrian capital for the first time.

The fierce fighting in Damascus came after a bombing killed three top officials, including the defence minister and a brother-in-law of President Bashar al-Assad on Wednesday in a blow to the heart of the regime.

State television aired footage Thursday of Assad with his new defence minister, Fahd al-Freij, the president's first public appearance since the attack.

It was the third time in nine months that Russia and China had used their powers as permanent members of the UN Security Council to block resolutions on Syria. There were 11 votes in favour, Russia and China's votes against and two abstentions.

“The United Kingdom is appalled at the veto of Russia and China,” said British Ambassador Mark Lyall Grant, whose country took the lead in drafting the resolution.

The text, backed by the United States, France, Germany and Portugal, called for non-military sanctions under Chapter VII of the UN Charter if Assad did not withdraw heavy weapons from Syrian cities in 10 days. Russia had said it could not accept sanctions.

France warned that the Chinese and Russian move threatened to end the peace mission of international envoy Kofi Annan.

“Refusing Annan the means of pressure that he asked for is to threaten his mission,” French Ambassador Gerard Araud told the council after the veto.

The United States said the Security Council had “utterly failed” on Syria and that it would now work outside of the council to confront Assad's regime.

“We will intensify our work with a diverse range of partners outside the Security Council to bring pressure to bear on the Assad regime and to deliver assistance to those in need,” said US Ambassador Susan Rice.

The Syrian army gave residents 48 hours to leave areas of the capital, where clashes are taking place between security forces and rebels pushing their “Damascus Volcano” offensive.

“These extremely violent clashes should continue in the next 48 hours to cleanse Damascus of terrorists by the time Ramadan begins” on Friday, a security source told AFP, referring to the Muslim fasting month.

The Britain-based Syrian Observatory for Human Rights watchdog said that in the western district of Mazzeh alone, hundreds of people were on the move, “fearing a large-scale operation by regime troops.”Residents also fled the southern district of Tadamon and the Palestinian refugee camp Yarmuk, it said.

“The army stormed the Qaboon district with a large number of tanks,” the Observatory's Rami Abdel Rahman told AFP. The situation “is worse than catastrophic,” one Damascus resident told AFP.

“The medical and humanitarian situation is getting worse.”The authorities announced that state funerals will held on Friday for the three regime officials killed in Wednesday's bombing.

“State funerals will be held in Damascus tomorrow, and then each of the bodies will be transported to his native town to be buried there,” a security source told AFP.

Assad's brother-in-law and one of the Syrian security apparatus' hawks, Assef Shawkat, will be buried in the western province of Tartus.

Defence minister Daoud Rajha will be buried in his Christian town of Maalula near Damascus, and crisis cell chief Hassan Turkmani in northern Aleppo.

Assad's mother Anissa and his sister Bushra -- Shawkat's widow -- were in Tartus, on the Mediterranean coast, to receive condolences but it was unclear whether Assad himself would attend the funerals.

As deputy defence minister and a former military intelligence chief, Shawkat was hated by the anti-regime opposition. He belonged to the Alawite community -- a Shia offshoot of Islam to which Assad's family also adheres.

The Observatory's Abdel Rahman said: “There is an escalation by the Syrian regime to avenge the operation that targeted the (security chiefs).

“The rebels have also escalated to reap the fruits of the attack, and to try to finish off the battle” for Damascus, he added.

A total of 107 were killed in violence on Thursday -- 47 soldiers, 42 civilians and 18 rebel fighters, according to the Observatory's figures.

“It pains me to say, but we are not on the track for peace in Syria, and the escalations we have witnessed in Damascus over the past few days is a testimony to that,” Major General Robert Mood, the head of the UN Supervision Mission in Syria, told reporters on Thursday.