Sudanese protesters on Tuesday defied their embattled president's ban on unauthorized public gatherings, with hundreds rallying across the country to call for his resignation.

The protests came despite a state of emergency imposed last Friday by President Omar al-Bashir in response to more than two months of demonstrations against his nearly three-decade rule. Nationwide protests erupted in December, initially over rising prices and shortages but quickly turned to calls for autocratic al-Bashir's ouster.

Tuesday's rallies were called by the Sudanese Professional Association, an umbrella of independent professional unions that has spearheaded the two and a half months of protests.

Video footage shows demonstrators, mostly women, marching in the streets of Khartoum's twin city of Omdurman. Demonstrations were also reported in the city of Atbara and the country's troubled Darfur region.

On Monday, al-Bashir issued decrees giving security forces powers to search buildings, restrict movements of people and public transportation, arrest individuals suspected of crimes related to the state of emergency and seize assets or property during investigations, according to the state-run SUNA news agency.

The decrees included a ban on unauthorized trading and stockpiling fuel products, prison terms from those travelling with more than $3,000 in cash or 150 grams of gold.

The unions said the state of emergency was unconstitutional and that they would challenge it in courts. ``We have one option, which is to win,'' they added, calling for fresh protests against al-Bashir.

``The ban is a desperate decision aiming at terrifying the protesters and their families,'' said rights lawyer Amal el-Zain. ``It may curb the uprising but will not stop it.''

Along with imposing the state of emergency, which is to last a year, al-Bashir disbanded the federal government and replaced all state governors with senior army officers. The order also gave security forces a free hand in cracking down on protesters and making arrests, and placed heavier restrictions on the press and opposition parties.

The moves by al-Bashir, who seized power in an Islamist-backed military coup in 1989, further concentrated power in his hands and set the stage for a bloody crackdown on protests, said the International Crisis Group.

The group urged the U.S. and the European Union not to normalize relations with Khartoum if it ``gives its forces carte blanche to kill and detain protesters.''

Al-Bashir's term expires in 2020; he has repeatedly promised not to run again. Without amending the constitution, he can't run for a third term.

Earlier this month, a parliamentary committee tasked with amending the constitution to scrap presidential term limits canceled its meetings, a move that appeared to be the only political concession by al-Bashir so far.

The unrest coincides with worsening economic woes that saw a currency devaluation, price hikes, fuel shortages and a steep rise in the price of bread, a main fare for most Sudanese.

Activists say at least 57 people have been killed in the protests. The government's latest tally stands at 30 killed, but figures have not been updated in weeks.