KHARTOUM, Sudan — Sudanese security forces have moved against a protest sit-in camp in the capital Monday, besieging the site and setting fire to tents, witnesses and protest leaders said. Machine-gun fire and explosions were heard and smoke rose from the area.

Protest organizers said at least five people were killed.

The military's move came after a weeks-long standoff with protesters seeking a speedy transition to civilian rule following the April ouster of long-time strongman Omar al-Bashir.

Dura Gambo, an activist, said large numbers of troops had besieged the sit-in area outside the military's headquarters in Khartoum on Monday and arrested protesters trying to leave.

Amal al-Zein, another activist, said security forces set fire to the tents in sit-in area. "They are surrounding the sit-in from all directions," she said.

The Sudan Doctors' Committee said at least five people were killed early Monday and an unspecified number had been wounded. The group said medical personnel and injured people were trapped in clinics in the area, and demanded that they be allowed to leave.

Earlier, a statement by protest leaders said the military is trying to disperse the sit-in, and urged supporters to come to the area.

Tens of thousands of protesters have been camped since April 6 outside the military's headquarters, the epicenter of Sudan's uprising that led to the military overthrow of al-Bashir.

Protesters vowed to remain in the streets after Bashir's ouster, saying an end to his 30-year rule did not go far enough.

Protest leaders and military officials have been negotiating over the makeup of a transitional government, as protesters call for "limited military representation" in a sovereign council that would lead the country as it transitions to civilian rule over three years.

Both sides are split over the makeup and leadership of the council, with the ruling generals refusing to relinquish power.