Human Rights Watch on Monday accused Sudanese government forces and allied militias of leading a campaign of killings and rapes in areas of Blue Nile state where they are battling insurgents.

Khartoum has been struggling to crush an insurgency in Blue Nile and neighbouring South Kordofan since 2011, when the Sudan Peoples Liberation Movement-North (SPLM-N) mounted a revolt.

"Sudanese government forces are getting away with abusive and illegal tactics under a guise of counterinsurgency, including rape, arbitrary detentions and killings," HRW's Daniel Bekele said in a report.

HRW's report was based on interviews with six internally displaced persons inside Blue Nile and 42 refugees who had fled to South Sudan.

The refugees said troops sexually assaulted women, arbitrarily detained and beat men and tried to force them to enlist in the armed forces, HRW reported.

"The number of rapes reported to us, often in harrowing detail, suggests that sexual violence is part of the government's counterinsurgency strategy," Bekele said.

Interviewees said regular Sudanese troops and pro-government militia were mostly behind the violence.

It was not possible to reach the Sudanese military for comment, and restrictions on travel to Blue Nile make it almost impossible to independently verify conditions there.

The rights watchdog urged the UN Security Council to "impose both an arms embargo on the government and targeted sanctions on individuals responsible for the abuses" in the Blue Nile and South Kordofan areas.

Talks between the SPLM-N and the government in Addis Ababa collapsed last week but the sides are due to meet again in January.

The SPLM-N rebelled against Khartoum in 2011, complaining that they were being marginalised and neglected by the Arab-based regime.

Sudan also faces another insurgency in the western region of Darfur, where rebels have been fighting the government since 2003.

In November, a local news website reported that government troops raped 200 women and girls in a village in the region, a charge which Khartoum has repeatedly denied.