At least five Sudanese protesters and a member of the security forces have died in clashes in the capital, Khartoum.
They were killed in gunfire at a sit-in outside military HQ where demonstrators are demanding full civilian government. Dozens have also been injured.
Protesters said soldiers were responsible, but the army blamed it on “unidentified elements”.
Sudan has been ruled by a transitional military council since last month’s toppling of President Omar al-Bashir.
It is unclear exactly what happened but activists have been talking about how they were targeted by a gunman.
“He shot a bullet at me, he was 20 metres away from me, at most,” Raed Mubarak told the Reuters news agency.
“He saw me, and he meant to shoot me. It was intentional. He did not even shoot at my leg or up in the air, he shot at my chest, at the left, intending to hit the heart. He meant to kill me.”
Demonstrators have been occupying the square in front of the headquarters since 6 April, five days before the president was overthrown by the military.
Initially, talks between the ruling generals and the protest organisers had shown little sign of progress.
However, just before Monday night’s violence, both sides announced they had agreed on the structure of a new administration.