"The two sides late Friday signed an extension of the ceasefire for the whole of this month starting May 1 to 31," retired Kenyan army general Lazaro Sumbeiywo said on Sunday, speaking from the peace talks venue in Naivasha, 80km north-west of Nairobi.
Despite the truce, mediators and UN officials last month said at least 70,000 people have been displaced in renewed fighting in south Sudan's Shilluk kingdom, an apparent violation of the ceasefire that was signed in October 2001.
The violence, which erupted in March, pits militia loyal to rebel leader Lam Akol, an SPLA member, against pro-government fighters.
Sudan's vice-president, Ali Uthman Taha, and SPLA leader John Garang resumed talks in Kenya on Wednesday in an attempt to unblock an impasse on whether Islamic law should be applied in the Sudanese capital, Khartoum, during a six-year transition period when the city will serve as the joint capital before a referendum on self-determination is held for the south.
In previous rounds, the two sides have agreed to equally share national resources, notably oil revenue, and Khartoum agreed to withdraw its massive troop presence from southern positions to pave the way for the creation of integrated army units.
The war in Sudan started in 1983 when the south, where most people observe traditional religions, took up arms to end domination by the wealthier Muslim and Arabised north.
The conflict, coupled by recurrent famine and disease, has claimed at least 1.5 million lives and sent more than four million others fleeing from their homelands.