There are multiple reports of gunfire being heard at the protest site in the centre of the Sudanese capital, Khartoum.
Reuters news agency is quoting witnesses and Arabic TV stations saying that security forces have entered the sit-in area.
Activists are quoted as saying that it was an attempt to disperse the protesters.
Videos are being shared on Twitter that appear to show people who have been injured, but these have not been verified.
The sit-in protest outside the military headquarters in Khartoum has continued as civilian leaders have been negotiating with the Transitional Military Council (TMC) over the make-up of the administration that will be in charge while the country prepares for democratic rule.
The military have tolerated the protests as long as they were taking place within a clearly defined area.
The TMC has governed Sudan since long-time President Omar al-Bashir was overthrown in April.
Source: bbc.com