Civil society groups in war-torn South Sudan warned Tuesday the country needs peace to hold elections, and said the government should extend its mandate rather than vote with conflict raging.

The government announced earlier this month presidential and parliamentary polls would be held in the bitterly divided nation between May and July, the first time elections would be held in South Sudan as an independent country.

The Sudanese military has been battling insurgents for control of parts of the conflict-stricken South Kordofan region, both sides said, giving conflicting reports of the situation there.

The fighting comes as Khartoum presses its latest offensive in the South Kordofan and Blue Nile areas and the western region of Darfur to try to end the conflicts wracking its peripheries.

Warring South Sudanese rivals met for Chinese-mediated talks in Khartoum on Monday, agreeing to "immediately work to stop hostilities," Sudan's foreign minister said.

The rivals also agreed to "speed up the pace of negotiations to form a transitional government," Sudanese Foreign Minister Ali Karti told reporters after the meeting.

Rebels in South Sudan slaughtered at least 353 civilians in April last year, including people sheltering in a mosque, hospital and a United Nations base, U.N. rights investigators said Friday.

The report is the first detailed account of two incidents that have highlighted a pattern of gross abuses and atrocities committed during the year-old civil war in the world's youngest nation.

Boko Haram's seizure of a key town and military base in Nigeria's far northeast has tightened its grip on the region, undermining efforts to tackle the insurgency, experts said on Tuesday.

The capture of Baga and the headquarters of the Multinational Joint Task Force (MNJTF) now means the Islamists control all three of Borno state's borders with Niger, Chad and Cameroon.

Sudan's parliament on Sunday passed constitutional amendments allowing President Omar al-Bashir to appoint state governors directly and expanding the mandate of its powerful security agency.

"The amendments were approved unanimously," national assembly speaker Al-Fatih Ezzedine Mansour said after parliament agreed to 18 changes.

Sudanese government forces and rebels have been battling for control of a strategic area in the war-torn Darfur region, the two sides say, giving conflicting reports on developments there.

In the latest operation to end the conflict in Darfur, the army said late Thursday its troops had driven  insurgents out of the Fanga area in the Jebel Marra region, killing at least 50 rebels and destroying 50 vehicles.

Sudan has ordered two senior United Nations officials to leave, a U.N. staff member said Thursday, after a recent spike in tensions between Khartoum and the peacekeeping mission in Darfur.

The U.N. resident coordinator and humanitarian coordinator Ali Zaatari and the U.N. Development Program country director Yvonne Helle were asked by the government to leave, the U.N. staffer said on condition of anonymity.

At least eight asylum-seekers have drowned trying to cross a river in Sudan during an attempt to smuggle them out of a refugee camp, the U.N. refugee agency said Thursday.

Sudan's electoral body said Tuesday it postponed elections to allow parliament to consider a constitutional amendment allowing President Omar al-Bashir to appoint state governors who were to have been elected.