JUBA (Reuters) - One South Sudanese lawmaker and two security personnel were killed in an ambush in the north-east of the country while returning from a peace mission, a ruling party spokesman said on Wednesday.

South Sudan, the world’s youngest nation, has been racked by civil war since 2013, when President Salva Kiir’s troops clashed with forces loyal to Riek Machar, the former vice president.

Kiir, Machar and other rebel factions signed an accord last September, halting the fighting.

Peter Lam Both, spokesman for Kiir’s SPLM party, said the incident had happened late on Tuesday when a group of lawmakers were attacked by fighters of the White Army militia in a village in Latjor state in a region formerly called Upper Nile.

The White Army is part of SPLA-IO, the armed wing of Machar’s SPLM-IO party.

Spokesman Both said the members of parliament had been sent by the SPLM Party to visit their constituencies to explain the peace deal to citizens.

“The MPs from Latjor state went to Mandeng and the meeting organized between the leadership of the SPLA-IO...and had a very good discussion with the Governor of the SPLM-IO,” Both said.

“After the meeting, they went back to their boat and were ambushed on the way and Hon. Simon Deng and two other people were killed and two others wounded,” Both told Reuters.

Lam Paul Gabriel, opposition deputy military spokesman rejected the suggestion of White Army involvement.

“That is anti-peace language, we were all attacked by criminals, these are not White Army. I totally deny that,” he said.

South Sudan’s civil war, often fought along ethnic lines, has crippled oil production, forced millions to flee and killed some 400,000 people.

Previous peace deals have quickly fallen apart.