KHARTOUM, Sudan — Sudan’s ruling military moved to crush the protest movement opposing its power as security forces overran the main sit-in site in the capital Monday, unleashing furious volleys of gunfire, burning down tents and killing at least 30 people, witnesses and protest leaders said.

With the assault, the generals signaled an end of their tolerance of the pro-democracy demonstrators, who for months have been camped outside the military’s headquarters as the two sides negotiated over who would run the country after the April ouster of longtime strongman Omar al-Bashir.

After they succeeded in forcing the military to remove al-Bashir, the protesters had stayed in the streets, demanding the generals move to the background and allow civilians to lead the transition.

The dispersal of the sit-in now risks escalating violence even further. Scattered by the bloody assault, protesters vowed to keep up their campaign, suspending talks and calling for a general strike and civil disobedience. They urged nighttime marches across the country.

“This is a critical point in our revolution. The military council has chosen escalation and confrontation,” said Mohammed Yousef al-Mustafa, a spokesman for the Sudanese Professionals’ Association, which has spearheaded the protests.

“Those are criminals who should have been treated like al-Bashir,” he said. “Now the situation is either them or us, there is no other way.”

The ruling military council said in a statement that security forces had been trying to clear an area adjacent to the protest camp when those it was chasing fled into the sit-in site, leading to the shooting deaths and injuries.

But activists said the assault appeared to be a coordinated move, with other forces attacking similar sit-ins in Khartoum’s sister city of Omdurman and the eastern city of al-Qadarif.

The attack came on the day before the Eid holiday that ends Ramadan, the holy month when Muslims fast during daylight hours. Large numbers of troops from the military, police and Rapid Support Forces — an elite unit that during the anti-al-Bashir protests had vowed to protect the sit-in — moved in on the gathering after overnight rains, activists said.

“They are surrounding the sit-in from all directions,” one activist, Amal al-Zein, said early in the assault, in which the forces burned tents and arrested those trying to flee.

An Associated Press journalist heard gunshots and explosions, and saw buses and soldiers on foot blocking roads leading to the protest site. In online videos, protesters were seen running and ducking as barrages of gunfire echoed. Smoke rose from tires set ablaze by the protesters.

The Sudan Doctors’ Committee put the death toll at 30 and said it was rising, although it was difficult to count in the area outside the military complex in Khartoum. Hundreds of people were wounded, many by gunfire, the group said.

In addition to calling for the nighttime marches, the Sudanese Professionals’ Association also called for closing off main roads to “paralyze public life” across the country.