Sudanese security forces used tear gas to disperse protesters on Sunday, as opponents of President Omar al-Bashir defied a state of emergency he declared on Friday and took to the streets again in cities across the country.

Opposition groups claim Bashir's decision was an attempt to silence popular demands he step down and called for protests to continue.

Anti-government demonstrations began on December 19, triggered by price increases and cash shortages, but quickly developed into protests against Bashir's rule.

Security forces fired tear gas at hundreds of protesters in the capital Khartoum and across the Nile River in Omdurman, witnesses said, as Bashir swore in officials he appointed to replace those he sacked when he dissolved the central and state governments on Friday.

Bashir posed for a photo with newly-appointed first vice president Awad Mohamed Ahmed Ibn Auf and new state governors, all wearing military uniforms after a swearing-in ceremony at the presidential palace.

The use of military garb sent the message that "the military authority is the one to assume the reins of power in a nationalistic way in the country," said Fath Alrahman Ahmed, a political science professor at  Neelain University.

Protests in Khartoum have escalated since the state of emergency was announced, and demonstrations were held on Sunday in various parts of the country.

It's said that security forces confronted about 1,000 protesters in the Banet neighborhood of Omdurman, where demonstrators had blocked streets with car tires.

In the Burri neighborhood of Khartoum, hundreds blocked a main road, setting fire to car tires and chanting: "Freedom! Freedom!", witnesses said.

There were also protests in the neighborhood of Maamoura in eastern Khartoum and Wad Madani, the capital of Gezira state.