KHARTOUM (Reuters) - Sudanese security forces clashed with protesters in three cities on Sunday as demonstrations against Omar al-Bashir’s rule continued for a fourth week, witnesses said.

In Khartoum North, across the Blue Nile from the center of the capital, security forces chased groups of protesters down side streets and fired tear gas to disperse demonstrations in several areas, a Reuters witness said.

They also confronted protesters with tear gas in Wad Medani, the capital of Gezira state, southeast of the capital, and for the first time in Nyala, the main city in South Darfur, witnesses said.

Protests triggered by an economic crisis have rippled across Sudan since Dec. 19 in the most sustained challenge yet to Bashir’s close to 30-year rule.

Security forces have used live ammunition and tear gas to break up demonstrations, as well as arresting protesters and opposition figures.

A government fact-finding committee has recorded 24 deaths and Amnesty International has said that at least 40 have died.

Officials have blamed the protests on “infiltrators” and said they are working to address economic problems.

In Khartoum North on Sunday hundreds of people braved a heavy security presence to protest despite police and other security personnel trying to clear the area ahead of the rally.

Some carried national flags and were chanting “freedom, freedom” and “with our soul, with our blood, we sacrifice ourselves for you Sudan”.

“We will continue to demonstrate until Bashir falls ... the country needs change,” one 36-year-old protester told Reuters.