Sudan's security forces have used sexual violence and intimidation to stop female activists from protesting and carrying out human rights campaigns, Human Rights Watch said on Thursday.

The powerful National Intelligence and Security Service (NISS) regularly detains rights workers and opposition politicians in Sudan but HRW said female activists faced additional dangers from the security services.

Gunmen killed a Chadian army officer serving in a joint unit patrolling Sudan's border with Chad in the war-torn region of Darfur, the Sudanese military said Thursday.

The joint force has operated in Darfur since 2010, seven years after ethnic minority insurgents in the western region rebelled against the Arab-dominated Khartoum government.

Sudan warned Thursday it could shut its border with South Sudan just weeks after reopening crossings, accusing Juba of backing insurgents battling Khartoum.

South Sudan became independent from Sudan in 2011 under a peace deal that ended a 22-year civil war, but Juba and Khartoum have traded allegations the other is supporting rebels on their territory, which both deny.

Indonesia's leader Monday held talks with Sudanese President Omar al-Bashir, who has been indicted for war crimes by the International Criminal Court, with Jakarta defending having invited him to a summit of Muslim countries.

Bashir met President Joko Widodo and the Indonesian foreign minister briefly on the sidelines of an Organization of Islamic Cooperation (OIC) summit in Jakarta.

Fighting raged for a second day Wednesday in the eastern South Sudan town of Pibor, injuring at least 35 people and forcing some 1,000 others to shelter in a U.N. base, medical charity MSF said.

The violence erupted on Tuesday in the town in Jonglei state, one of the flashpoints in the civil war which has torn the world's youngest nation since December 2013.

Amnesty International on Wednesday condemned countries in southern Africa for treating anti-government activists as "criminals" while hosting leaders accused of genocide such as Sudanese President Omar al-Bashir.

"Whilst activists in Angola, Swaziland and Zimbabwe were rounded up on the streets, Sudan's President Omar al-Bashir was permitted to travel unhindered to the AU (African Union) conference in South Africa," the rights agency said in its annual report.

South Sudan's President Salva Kiir has named his arch-rival Riek Machar as vice-president, raising hopes for the implementation of a repeatedly broken peace deal to end more than two years of civil war.

Tens of thousands of people have been killed and over two million forced from their homes since war between the rivals broke out in December 2013, pushing the world's youngest nation to the brink of famine.

They came for a night fleeing fighting, hammering on the gates of the United Nations base as gunmen rampaged through South Sudan's capital killing and looting.

Two years later, over 185,000 people are sheltering inside U.N. camps across the country, still too frightened to leave.

Peace talks between Sudan's government and rebels have adjourned without a deal after a week of negotiations in Ethiopia, African Union mediators said Tuesday.

Rebel factions from the war-torn western Darfur region as well as the Sudan People's Liberation Movement-North (SPLM-N), fighting the government in the southern Blue Nile and South Kordofan states since 2011, met with government delegates from Khartoum.

Weeks after U.N.-backed experts warned that thousands are dying of starvation in South Sudan war zones, aid agencies say they cannot access areas to stave off famine because of "spiraling" violence.

Last month, U.N. agencies said 30,000 people were starving to death in Unity state, with Integrated Food Security Phase Classification (IPC) experts warning of a "concrete risk of famine" before the end of the year if fighting continues and aid does not reach the hardest hit areas.