Sudanese security forces Tuesday fired tear gas at thousands of anti-government protesters demonstrating outside the army headquarters in Khartoum for a third night, with gunshots also heard, witnesses said.

Witnesses and a protester said security forces of the powerful National Intelligence and Security Service and riot police were firing tear gas in a bid to disperse the demonstrators from the military complex.

They said it was unclear who was firing the gunshots.

Thousands of protesters have massed at the complex since Saturday, urging the military to back them in demanding the resignation of President Omar al-Bashir.