In a statement, the European Union's top diplomat Catherine Ashton said Brahimi was "an experienced diplomat with a deep understanding of the region."

"The EU will provide him with its full support in this immensely challenging task," Ashton said in the statement.

The United Nations announced the appointment of Brahimi, a former Algerian foreign minister, as joint UN-Arab League envoy on Friday. He replaces Kofi Annan, who quit at the start of August complaining of a lack of international support for his peacemaking endeavors.

Ashton joined UN chief Ban Ki-moon in calling for more support for the special envoy this time round, saying: "The prerequisite for any political process to work is full support by the UN Security Council and agreement by all parties to give diplomacy another chance."

International divisions

Diplomatic efforts on Syria have been hampered by rifts in the Security Council, with notably Russia and China opposing sanctions on Syrian President Bashar Assad over his government's bloody crackdown on a 17-month uprising.

Both China and Russia have, however, also welcomed Brahimi's appointment, saying they would support him and cooperate with his mission.

United States Secretary of State Hillary Clinton gave her country's backing to Brahimi, saying the world community was committed to bringing about change in Syria.

The 78-year-old Brahimi has long experience in dealing with countries involved in conflict, having been UN envoy in Afghanistan and Iraq. He also helped end the Lebanese civil war in the 1980s as Arab League representative, when he negotiated with the Syrian government of the time.

However, the Nobel Peace laureate has expressed doubts as to whether he will be able to resolve the Syrian conflict. Asked whether he was confident of success, he told the France 24 news channel: "No, I'm not. What I am confident of is that I am going to try my utmost, my very, very best."

Worsening humanitarian situation

This comes as activists report intensified fighting in several key Syrian cities.

The British-based Syrian Observatory for Human Rights said war planes bombed the town of Aazaz on Friday just days after another airstrike that killed at least 40 people.

It said Syrian government forces also bombarded several areas of the key northern commercial hub, Aleppo, as well as rebel-held districts in the central city of Homs and the southern city of Herak.

A total of 129 people were killed on Friday alone, it said.

The conflict is causing an ever-growing exodus of refugees from Syria, with the UN saying at least 170,000 have now fled the country, many of them to Turkey, where 66,000 Syrians are said to have taken refuge.

Others are sheltering in Jordan, Lebanon and Iraq.

Humanitarian conditions have also worsened in Syria itself, with UN agencies warning that the fighting is cutting civilians off from food supplies and health assistance. UN officials say some 1.2 million people have been displaced within the country.

Defection of vice president denied

Meanwhile, Syrian state TV has denied reports that Vice President Faruq al-Shara had defected.

"Mr. Shara has never thought about leaving the country or going anywhere," it said. It aired no footage of the 73-year-old, but quoted from a statement in which Shara also welcomed Brahimi's appointment.

Assad's prime minister, two members of his cabinet and several diplomats have already defected.

tj/msh (AFP, Reuters, dpa)