A prominent Sudanese human rights group has accused the country's army and security forces of torturing people to death and operating "execution chambers".

The Emergency Lawyers group said it had documented hundreds of arrests in the capital, Khartoum. It said that in the "worst cases", some captives had later been found dead with evidence of torture.

The Sudanese army recaptured the city from the paramilitary Rapid Support Forces (RSF) in March, against which it is fighting a bitter civil war that has killed tens of thousands in two years.

The army did not respond to the BBC's request for comment on Sunday.

Throughout the war, the Emergency Lawyers group has documented atrocities by both the army and the RSF.

In a statement on social media platform X, Emergency Lawyers said it had observed a "dangerous escalation in violations".

Some detainees were arrested at random and taken to large detention centres, the group alleged.

"Their fates range from continued detention in inhumane conditions, trials conducted by security agencies that lack the most basic standards of justice, or release in poor health," the statement said.

"In the worst cases, some are found dead after being killed or declared dead as a result of torture."

The use of torture was common during the oppressive rule of president Omar al-Bashir.

Throughout the current war, the RSF have also been found to have abused and executed prisoners.

The UN Independent International Fact-Finding Mission for the Sudan said in March that both sides were responsible for "a widespread pattern of arbitrary detention, torture and ill-treatment of detainees".

It said both both the RSF and the army had used "rape and other forms of sexual violence, arbitrary arrest and detention, as well as torture and ill-treatment".

The fighting has sparked one of the world's worst humanitarian crises - 12 million people have been forced from their homes and famine has been declared in parts of the country.

Last week, medical charity Doctors Without Borders (MSF) said the war has fuelled the worst cholera outbreak the country has seen in years.

There have been nearly 100,000 cases of the disease and 2,470 deaths over the past year.