TRIPOLI, Libya - The western Libyan city of Misrata came under heavy bombardment on Sunday by forces loyal to Muammar Gadhafi, a rebel spokesman said.

Government forces had retreated in the coastal city of Misrata after a siege of nearly two months and rebels fighting to overthrow Gadhafi had claimed victory there on Saturday.

"The situation is very dangerous," rebel spokesman Abdelsalam said by telephone from Misrata.

"Gadhafi's brigades started random bombardment in the early hours of this morning. The bombardment is still going on. They targeted the city center, mainly Tripoli Street, and three residential areas."

He gave no indication of casualties in the bombardment. Hundreds of civilians have been killed in the fighting for Misrata.

Pope Benedict XVI on Sunday urged "diplomacy and dialogue" instead of arms.

"In the current conflict in Libya, may diplomacy and dialogue take the place of arms," the pope said in his traditional Easter message.

Addressing tens of thousands of pilgrims gathered in a sun-drenched St Peter's Square and millions watching on television worldwide, the pope added: "In the countries of northern Africa and the Middle East, may all citizens, especially young people, work to promote the common good."

Meanwhile, Libyan tribal leaders are trying to get rebels in Misrata to lay down their arms within 48 hours, a government official said early on Sunday.

If negotiations fail, Deputy Foreign Minister Khaled Kaim said tribal chiefs may send armed supporters into the city of 300,000 to fight the rebels.

However, the Misrata area is not known to have very large or dominant tribes, and rebels in the city questioned how much support Gadhafi had among them. It is also unclear whether the rebels would be willing to negotiate, particularly after claiming to have forced government forces to retreat. Kaim said tribal chiefs are still trying to get in touch with the rebels.

In another diplomatic development, Russia and Greece held talks with the Libyan government about the enforcement of a ceasefire, the official JANA news agency said.

JANA said Russian Foreign Minister Sergei Lavrov told Libyan Prime Minister Al-Baghdadi Al-Mahmoudi on Saturday Moscow could send observers to monitor a ceasefire and pave the way for a peaceful solution.

The official JANA news agency said Lavrov made the proposal during phone talks with Mahmoudi.

Mahmoudi also talked with his Greek counterpart George Papandreou and "reiterated Libya's commitment to United Nations resolutions" and said Libya is committed to the African Union's peace initiative.

The Libyan government has repeatedly made calls for ceasefires, rejected by rebels who say they are not matched by its actions.

Reuters-AP-AFP