Summit in Cairo forces Egypt's Morsi into the spotlight.

Leaders of Muslim nations called for a negotiated end to Syria's civil war at a summit in Cairo on Wednesday, thrusting Egypt's new Islamist president to center stage amid turbulence at home.

On the summit sidelines, the leaders of Egypt, Turkey and Iran gathered for talks on the Syria crisis. The Iranian foreign minister came out of the meeting expressing optimism about the prospects for a resolution.

The head of the Syrian opposition, in Cairo but not at the summit, told BBC Arabic that Iran was making the decisions in Damascus, and gave the Syrian government until Sunday to release female detainees or else his offer of talks would lapse.

The summit of the 57-member Organization of Islamic Cooperation opened the day after the assassination of a leading Tunisian opposition politician.

Tunisian President Moncef Marzouki cancelled his trip to the Cairo meeting after Shokri Belaid, a staunch secular opponent of the moderate Islamist government, was shot dead outside his home, triggering street protests.

With Iranian President Mahmoud Ahmadinejad making an ice-breaking visit to Egypt, the first by an Iranian leader since the 1979 Islamic revolution, the two-day meeting was focusing on how to stop the bloodshed in Syria, where President Bashar al-Assad counts Teheran as one of his allies.

In a keynote address, Egyptian President Mohammed Morsi called on the government in Damascus to learn the lessons of history and not put its interests above those of the nation, saying that rulers who did so were inevitably finished.

Morsi urged all OIC members to support the Syrian opposition's efforts to unite and bring about change.

Heavy fighting erupted in Damascus on Wednesday as rebels launched an offensive against government forces, breaking a lull in the conflict, opposition activists said.

Ahmadinejad earlier told Egyptian journalists there could be no military solution and he was encouraged that the Syrian government and opposition were moving toward negotiations to end a conflict in which at least 60,000 people have died.

Iranian Foreign Minister Ali Akbar Salehi told Egypt's state news agency he believed the Syrian government was ready to negotiate with the opposition. "We are optimistic," he added after the meeting with the leaders of Turkey and Egypt.

In an interview with BBC Arabic on Wednesday, opposition Syrian National Coalition leader Moaz Alkhatib said Iran was the real power in Damascus. Alkhatib had on Sunday offered to meet Syrian Vice-President Farouq al-Shara for peace talks if the authorities released thousands of prisoners.