New international mediator Kofi Annan urged all sides in the Syria crisis on Friday to cooperate with his mission, saying he was determined to put an end to the violence and human rights abuses.

"I look forward to having the full cooperation of all relevant parties and stakeholders in support of this united and determined effort by the United Nations and the Arab League to help bring an end to the violence and human rights abuses, and promote a peaceful solution to the Syrian crisis," he said.

Amnesty International demanded on Friday that aid agencies be given immediate access to Homs and other besieged Syrian protest cities, as world powers gathered in Tunisia to discuss the bloodshed.

The London-based human rights watchdog said it had received the names of 465 people reported killed in Homs since regime forces began pounding rebel neighborhoods of Syria's third-largest city three weeks ago.

A Syria-based opposition group said it was boycotting the international "Friends of Syria" meeting being held on Friday in Tunis on the future of the country, complaining of exclusion and fearing escalated militarization.

The National Coordination Committee for Democratic Change (NCCDC) denounced what it described as attempts to leave the door open to militarize the uprising against the regime of Bashar Assad, and for foreign military intervention.

French ambassador to Syria Eric Chevallier has returned to Damascus more than two weeks after being recalled in response to the Syrian government's crackdown on dissent, the embassy said on Friday.

"I can confirm that the ambassador of France returned to Damascus on Thursday night," a spokesman told Agence France Presse.

Israeli warplanes launched two air strikes on the Gaza Strip early Friday, the military said; hours after Palestinian militants fired two rockets at southern Israel.

"Israeli army aircraft thwarted an attempt by a terrorist squad to fire rockets at Israel from the northern Gaza Strip," an army statement said.

The U.N. named its former leader Kofi Annan as special envoy for Syria on the eve of an international conference Friday aimed at pressuring the Assad regime to halt the rising spiral of violence.

Amid international outrage over the deaths of two Western journalists and reports of intensified shelling of civilians, Annan was called on to represent both the U.N. and the Arab League in ending "violence and human rights violations, and promoting a peaceful solution to the Syrian crisis," the two bodies said in a statement Thursday.

U.S. Secretary of State Hillary Clinton said the Syrian National Council will demonstrate at international talks in Tunis on Friday that there is an alternative to President Bashar al-Assad's regime.

"We believe that the Syrian National Council, which will be there sitting at the table, will show that there is an alternative to the Assad regime, one that respects the rights of all Syrians," she told reporters in London on Thursday.

Seven Syrian activists collaborating with the Avaaz action group were found "executed" in Homs, while two others, including a foreigner, remain missing, the non-governmental organization said Thursday.

The group of nine men, including one foreign paramedic, had set off on foot for Baba Amr on Wednesday morning after hearing that two foreign journalists were killed in the flashpoint district of Homs, said Avaaz's Alex Renton.

Palestinian President Mahmoud Abbas and his rival Hamas leader Khaled Meshaal on Thursday postponed talks on forming a unified government, a Fatah official said, in a further delay to ending an almost five-year rift.

The official with the Abbas-led party said the talks were postponed "because Hamas continues to prevent the election committee from registering voters in Gaza," the Islamist-ruled Palestinian territory.

Russia and China on Thursday rejected pressure to change their position on Syria after vetoing a United Nations resolution condemning the Damascus regime for its bloody crackdown on the opposition.

Russian Foreign Minister Sergei Lavrov called his Chinese counterpart Yang Jiechi to discuss the two powers' future strategy on the crisis, less than a month after the U.N. Security Council vote.