Damascus on Sunday blasted a "Friends of Syria" meeting in Istanbul that is seeking ways to up the pressure on President Bashar Assad's regime as a "platform for the enemies of Syria."

"Only the naive and those who want to see through the eyes of the Americans believe that this is a conference for the friends of the Syrian people," said Al-Baath newspaper, mouthpiece of Assad's ruling party of the same name.

Iran on Sunday backtracked on reports that five Iranian "engineers" abducted in Syria had been freed -- the second time in months it retracted news of their liberation.

Kazem Sajjadi, a foreign ministry official in charge of Iranians abroad, told state television that five Iranian pilgrims who had been kidnapped separately had been released, but that the five engineers remained captives.

Al-Qaida suspects killed seven policemen in an attack on a checkpoint in southeast Yemen on Sunday, a security official said, a day after clashes between the army and militants left 40 dead.

"A group of Al-Qaida terrorists in two vehicles opened machinegun fire on a checkpoint killing seven policemen" in Shibam, a town in the southeastern province of Hadramawt, the official told AFP.

The U.N. must act to stop the violence in Syria, a major conference heard Sunday as bloodshed on the ground claimed more lives.

The head of the Arab League Nabil al-Arabi called on participants of the "Friends of Syria" conference to "simultaneously call on the Security Council to take a binding decision ... to stop the violence in Syria."

Egypt's Muslim Brotherhood is to field its deputy chairman Khairat al-Shater as a candidate in the upcoming presidential election, the group's party and supreme guide said on Saturday.

"The parliamentary bloc of the Freedom and Justice Party will nominate Khairat al-Shater as a candidate for the presidency," the FJP said on its Facebook page.

Syrian opposition leader Burhan Ghalioun said a "Friends of Syria" conference that opens in Turkey on Sunday must back the arming of rebels.

"The Syrian National Council expresses the demands of the Syrian people," Ghalioun told the press. "We have repeatedly called for the arming of the Free Syrian Army.

The United States and Gulf Arab states on Saturday urged envoy Kofi Annan to produce a "timeline for next steps" in his peace plan for Syria if President Bashar Assad fails to stop the bloodshed.

U.S. Secretary of State Hillary Clinton, who met her counterparts from Saudi Arabia, Kuwait, Bahrain, Qatar, the United Arab Emirates and Oman at a meeting in Riyadh, voiced concern over Syria's continued deadly crackdown on dissent.

Expectations are low of an international conference Sunday in Istanbul having much impact on the Syrian crisis, as discord among the so-called "Friends of Syria" outweighs their agreements.

More than 70 representatives from Western and Arab countries will gather to craft a solution aimed at halting the killing in Syria, after more than a year that has left between 9,000 and 10,000 people dead in a crackdown on dissent by Bashar Assad's regime.

At least 16 people were killed on Saturday in new clashes between the Toubou people and Arab tribesmen in the southern Libyan desert oasis of Sabha, local and medical sources told Agence France Presse.

A doctor at Sabha hospital, treating Arab casualties, said eight people were killed and another 50 wounded in fighting between the early morning and noon. A Toubou tribal source said eight of their people were also killed.

Violence across Syria killed at least 25people on Saturday as security forces fired at a Damascus funeral for protesters who died the previous day during demonstrations, monitors said.

The Syrian Observatory for Human Rights said a child was killed on Saturday by rocket fire in the Bayada area of Homs, where troops fired shells at rebels in its Khaldiyeh district at the rate of one a minute.