Sudanese soldiers intervened to protect several thousand demonstrators calling for an end to President Omar al-Bashir's rule on Monday after security forces tried to break up the sit-in, witnesses and activists said.
For the first time in some three months of unrest, a group of prominent opposition leaders joined protesters outside the defence ministry in Khartoum. They addressed demonstrators who have been massed for two days outside the ministry compound and repeated their demand for Bashir and his government to step down immediately, witnesses said.
The compound also includes Bashir's residence and the secret service headquarters.
The interior minister told parliament that six people had been killed on Saturday and Sunday in disturbances in the capital, and one in the western region of Darfur.
Frequent protests have been staged in Sudan since December, when the government tried to raise bread prices, building into the most sustained challenge yet to Bashir, a former army general who came to power in a military coup in 1989.
On Saturday, protesters marched towards the defence ministry hoping to deliver a memorandum urging the army to side with them. They reached the ministry compound despite attempts by security forces to stop them, and set up a camp.
Numbers outside the compound continued to grow on Monday despite the closure of all roads leading there, witnesses said.
United Nations Secretary-General Antonio Guterres urged all parties to "exercise utmost restraint and avoid violence", and called for the release of detained protesters, U.N. spokesman Stephane Dujarric said.
Early on Monday, witnesses and activists said riot police and secret service personnel charged the demonstrators with pickup trucks while firing tear gas, trying to disperse a crowd estimated at 3,000 men and women.
But witnesses and activists said soldiers guarding the compound had come out to protect the demonstrators, firing warning shots in the air.
The security forces retreated without firing back and soldiers deployed around the area, while demonstrators chanted "The army is protecting us" and "One people, one army", witnesses said. There were no immediate reports of casualties.
Information Minister Hassan Ismail, who is also the government spokesman, contradicted the reports.
"The crowd in front of the (military) general command has been cleared completely, in a way that resulted in no casualties among all parties."
Previous attempts by security forces have failed to disperse the protesters, who have vowed to stay until Bashir steps down.
Addressing a meeting of military commanders, Bashir's defence minister and vice president said security forces would not permit attempts to divide them, state news agency SUNA reported.
Bashir is wanted by international prosecutors for alleged war crimes in the western Darfur region, and demonstrators accuse him of presiding over years of repression and promoting policies that devastated the economy.
The government denies any connection with atrocities in Darfur and blames U.S. sanctions for the economic hardships.
Bashir has acknowledged that the protesters have legitimate demands but says they must be addressed peacefully, and through the ballot box.
Security forces have used tear gas, stun grenades and mass arrests, and have sometimes fired live ammunition.
Authorities have also blocked social media. Facebook and WhatsApp, the most popular platforms in Sudan, have been inaccessible without a virtual private network since Sunday, residents said.
In his address to parliament, Interior Minister Bishara Jumaa said 39 people had died since the onset of the protests, including three members of the security forces.
He said 10,000 protesters had gathered outside the defence ministry compound on Saturday, the first time authorities had provided such a crowd estimate.
Activists put the death toll at more than 60 since the protests began. They chose Saturday for their march to coincide with the April 6 anniversary of a 1985 military coup that forced long-time autocrat Jaafar Nimeiri to step down after protests.