Heavy gunfire was heard at a protest outside the Defence Ministry in Sudan’s capital Khartoum on Tuesday, live broadcast by Arab TV stations showed,
The activists also said that security forces were trying to break up the protest by force.
Activists said in a statement posted on social media that army soldiers guarding the ministry were trying to protect the demonstrators and opened the gates of the compound to give sanctuary.
Both Al-Hadath TV and Al Jazeera broadcast live footage in which heavy gunfire was heard and people were seen running for cover.
They reported an attempt by security forces to disperse the demonstrators.
There were reports that at least two government soldiers were killed, but it was not immediately possible to verify.
Sudan has been rocked by months of small but persistent protests that were sparked by bread price rises and cash shortages.
The demonstrations later turned against President Omar al-Bashir, a former paratrooper, who had been in office since 1989.
Bashir, who is being sought by international prosecutors for alleged war crimes in the country’s western Darfur region, has refused to step down and said his opponents needed to seek power through the ballot box.
The protests escalated on Saturday, when activists, trying to push the country’s armed forces to side with them, marched towards a compound in the centre of the capital housing the defence ministry.
The protesters also marched toward Bashir’s residence and the country’s security headquarters and camped out there.
Activists said 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.
Security forces have made several attempts to break up the protest, but army soldiers have repeatedly come out to protect the demonstrators, often firing shots in the air and deploying soldiers on streets around the protesters.
The interior minister, Bishara Jumaa, told parliament on Monday that six people had been killed on Saturday and Sunday in disturbances in the capital, and one in the western region of Darfur.
He also said that 15 civilians and 42 members of the security forces were injured in the protests and 2,496 protesters were arrested in Khartoum.
UN Secretary-General, Antonio Guterres, on Monday urged all parties in Sudan to “exercise utmost restraint and avoid violence”, and called for the release of detained protesters, UN spokesman, Stephane Dujarric, said.
Jumaa said 39 people had died since the onset of the protests, including three members of the security forces. Activists put the death toll at more than 60.
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.