N'DJAMENA - Chad's government and four Sudan-based Chadian rebel groups signed a "definitive peace accord" in Libya on Thursday that included an immediate ceasefire, a Chadian presidency official said.

The deal, which aimed to end more than two years of sporadic fighting in eastern Chad, was signed in the Libyan city of Sirte in the presence of Chadian President Idriss Deby, Sudanese President Omar Hassan al-Bashir and Libyan leader Muammar Gaddafi, the official, who asked not to named, told Reuters.

It came before Libya was due to host peace talks on Saturday between Sudan's government and some rebel groups from the Sudanese Darfur region, whose four-year-old conflict has spilled over the border into neighbouring Chad.

Chad announced the peace accord weeks before the planned deployment in its violence-torn east of a European Union peacekeeping force which will aim to protect civilians, refugees and foreign aid workers from militia and rebel raiders.

"The government of the Republic of Chad and the four main rebel movements based in Sudan have signed tonight in Libya a definitive peace accord," the Chadian official said.

The accord foresees an immediate ceasefire and the setting up of a committee to decide on the integration of members of the rebel groups into Chadian state structures.

The rebel groups who signed the deal, which included the Union of Forces for Democracy and Development (UFDD) led by Mahamat Nouri and the Assembly of Forces of Change (RFC) led by Timan Erdimi, have fought a hit-and-run guerrilla war against Deby's government in the east for more than two years.

The other rebel movements who signed were the Chadian National Concord (CNT) and the UFDD-Fundamental faction.

On Oct. 3, the four insurgent Chadian groups and Deby's government had initialled a preliminary outline peace deal brokered by Libya.

But some of the rebel leaders had subsequently criticised that preliminary deal as incomplete, saying the terms for disarmament and reintegration of their forces into the Chadian military had not been resolved.

It was not immediately clear whether these points had been resolved in the latest deal announced by the government.

"The agreement foresees among other things an immediate ceasefire, the rebel movements holding their current positions (on the ground) and the setting up a joint committee to determine the participation of the signatory groups in every level of the executive power," the Chadian official said.