Members of the armed forces install concertina razor wire as protesters gather outside the military headquarters in Khartoum on Sunday. AFP

Security forces killed at least five protesters in fresh anti-government marches in Sudan, in what organisers said was among the largest turnouts in three months.

Thousands of protesters rallied outside the army's headquarters in the capital on Sunday for a second day calling on the military to back them in demands that President Omar Al Bashir resign as police fired tear gas to disperse them.

Chanting "Sudan is rising, the army is rising," crowds of men and women massed outside the complex that also houses Bashir's official residence and the defence ministry, many of them having spent the night there, witnesses said.

"After what we did yesterday, we will not leave this area now until our mission is accomplished," said protester Osama Ahmed, who spent the night outside the compound.

"We won't leave this area until he steps down," he said, referring to Bashir.

Protesters whistled and waved at military vehicles entering the compound, prompting some soldiers to wave back, a day after demonstrators said they were gathering to ask the army to "come join us."

Riot police deployed near the complex Sunday morning, firing tear gas to disperse the crowds, a witness told AFP.

A protester waves the national flag outside the military headquarters in Khartoum on Sunday.  AFP

Security forces have responded to the protest movement with a fierce crackdown, killing at least 60 people according to Physicians for Human Rights, a New York-based rights group. The latest deaths raised the tally to at least 65 since protests began.

The government has said that 32 people have been killed, but hasn't updated its tally in weeks.

The rallies are being led by the Sudanese Professionals Association, an umbrella group of independent professional unions.

Sarah Abdel-Jaleel, a spokeswoman for the SPA, told The Associated Press that four people were killed in the capital city of Khartoum and another protester was killed in the neighbouring city of Omdurman.

Stone-throwing protesters clashed with security forces using tear gas, live ammunition and batons to disperse tens of thousands of people gathered outside the military's headquarters and a presidential residence in Khartoum, according to the organisers.

The Sudan Doctors Committee, an SPA affiliate, said that dozens had been wounded in rallies across the country, many of them by live ammunition.

The state-run SUNA news agency on Saturday quoted police spokesman General Hashim Abdel-Rahim as saying that one person was killed "during disturbances in Omdurman." He called the protests "illegal gatherings."

Bashir has offered little in the way of concessions, beyond calling for a national dialogue and asking parliament to postpone constitutional amendments that would allow him to seek a new term in next year's elections.


Agencies