International envoy Kofi Annan on Friday urged the world to raise the level of pressure on Syria's rival sides and said Iran should have a role to play in the effort.

"It's time for countries of influence to raise the level of pressure on the parties on the ground and to persuade them to stop the killing and start the talking," he told a press conference in Geneva.

The Egyptian Muslim Brotherhood's presidential candidate Mohamed Morsi said on Friday his movement wanted neither "confrontation nor violence," as the country nervously awaits the results of a divisive election.

Morsi spoke after the ruling military warned that it would deal "firmly" with any attempt to harm the public interest as thousands of people packed Cairo's Tahrir Square accusing it of a power grab.

Saudi female activists have cancelled their plan to brave a driving ban on Friday, settling instead for petitioning King Abdullah to allow them to get behind the wheel, members of their group said.

"I think that last year's attempt by ladies to drive in public has sent the message ... Now it's time to address officials to urge them to issue driving licenses to women," said researcher Hala al-Dosari.

Russian Foreign Minister Sergei Lavrov on Friday met his Syrian counterpart Walid al-Muallem, urging Damascus to do more to implement the plan of peace envoy Kofi Annan.

Turkey searched for a missing fighter-jet and held an emergency security summit Friday, as the prime minister backed off reported comments suggesting Syria had downed the aircraft.

The military plane -- reportedly an F-4 Phantom with two pilots aboard -- lost radio contact and vanished off radar screens around 0900 GMT over the eastern Mediterranean, near the border with Syria.

Egypt's ruling military warned on Friday that it would deal "firmly" with any attempt to harm the public interest as thousands of people packed Cairo's iconic Tahrir Square accusing it of a power grab.

The Supreme Council of the Armed Forces (SCAF), which took over when veteran strongman Hosni Mubarak was ousted by a popular uprising in February last year, also delivered veiled criticism of the Muslim Brotherhood, charging that efforts were afoot to pre-empt the outcome of a hard-fought presidential election.

The French Foreign Ministry called Friday for the Syrian military to desert en masse the day after a Syrian air force colonel defected after landing his MiG fighter in Jordan.

"Yesterday's defection leads us to call on members of the Syrian army and security forces to continue these defections, these desertions and no longer to obey the Damascus regime's criminal orders," ministry spokesman Bernard Valero told journalists.

Syrian protesters took to the streets on Friday as the government accused rebels of carrying out a "brutal massacre" of 25 of its supporters, and activists said regime forces killed at least 55 people across the country.

The independent Syrian Observatory for Human Rights gave a higher toll for the pro-regime losses, saying at least 26 government supporters -- most of them members of the feared shabiha militia -- had been killed.

Ankara denied Friday allegations that it is shipping weapons to Syrian rebels across the border, after a report claimed Turkey was among nations arming rebels fighting the regime in Damascus.

"Turkey does not ship weapons to any neighboring country, including Syria," foreign ministry spokesperson Selcuk Unal said when asked whether Turkey was involved in an alleged arms delivery to Syrian rebels.

Syrian troops clashed with rebels in the third-largest city Homs Friday, scuppering a new bid to rescue trapped civilians as the United Nations said up to 1.5 million people were now in need of aid.

The fresh bombardment of the central, Orontes valley city came after at least 168 died on Thursday, the highest single-day death toll since a U.N.-backed ceasefire was supposed to take effect on April 12, a human rights watchdog said. Activists in Homs reached by Agence France Presse via Skype spoke of a "catastrophic situation" in the historic centre and adjacent neighborhoods.