Political leaders representing warring factions in Libya signed a UN-brokered agreement on Sunday to cease fighting and form a unity government with a one-year mandate.

UN Special Envoy Bernardino Leon called the agreement between the factions an "important step" for Libya's future.

"This agreement will bring a step, an important step in the road of peace in Libya," Leon said at a ceremony in the Moroccan coastal town of Skhirat, where political leaders signed the agreement.

However, an important party in the Libyan conflict was missing from the agreement. The Islamist-dominated government in Tripoli - running a parallel parliament to the internationally-recognized one based in the eastern coastal city Tobruk - said they did not understand why the agreement was signed.

"We are still in the dialogue, but we don't really understand why they are rushing to sign before all the parties agree," Mowafaq Hawas, a representative of the General National Congress (GNC) in Tripoli, told the Reuters news agency.

Meanwhile, some representatives from municipalities in Tripoli initialed the deal alongside others allied to the armed alliance "Libya Dawn," which took control of Libya's capital a year ago.

"Let me enhance one message: The doors will remain open for those who have chosen not to be here," Leon said during the ceremony, referring to the rival government in Tripoli.

Negotiators are expected to meet following the Ramadan holiday to hash out the detail of the unity government.

The deal lays out the foundation of the government through the formation of a council of ministers headed by a prime minister and two deputies - forming the executive authority - and complimented by the House of Representatives, making up the legislative body.

Libya has been drawn into a years-long conflict between warring militias following the toppling and subsequent assassination of former dictator Moammar Gadhafi in 2011.

The "Islamic State" militant group has taken advantage of the security vacuum in the country by executing Christians and attacking embassies.

ls/jr (AP, AFP, Reuters, EFE)