Evidence of torture found as detention centre and mass grave discovered outside Khartoum

Exclusive: What appears to be a vast burial site found at former Rapid Support Forces base in Sudan, while rescued detainees speak of torture, starvation and deaths of fellow inmates

• Here you will die': detainees speak of executions, starvation and beatings at hands of Sudan's Rapid Support Forces

More than 500 people may have been tortured or starved to death and then buried in a secret mass grave north of Khartoum, according to evidence seen by the Guardian.

A visit to a base belonging to the paramilitary Rapid Support Forces (RSF) shortly after it was retaken by the Sudanese military found a previously unknown detention centre, with manacles hanging from doors, apparent punishment chambers and bloodstains on the floor. Accounts from people held at the detention centre describe being repeatedly tortured by their captors.