At least nine people have been killed and several others injured after Sudanese security forces stormed a protest camp in central Khartoum early Monday.
"The protesters holding a sit-in in front of the army general command are facing a massacre in a treacherous attempt to disperse the protest," said a statement from the main protest group.
Sudan's military has so far made no statements.
The protest outside the military headquarters has been the centre of a campaign to bring a civilian government to power.
Talks between protesters and Sudan's military rulers over the transitional period has ended in a deadlock over who would dominate the top decision-making body.

Trump oversees Thailand-Cambodia ceasefire agreement
Thailand's Queen Mother Sirikit dies at 93
Louvre transfers jewels to Bank of France after heist
Russian aerial attack on Kyiv kills two, injures 13, Ukraine officials say
Thai PM to sign Cambodia ceasefire deal, cuts short ASEAN trip after royal death
