CAIRO (AP) — A one-day strike shuttered business and emptied streets in the Sudanese capital, Khartoum, and other parts of the country on Tuesday, activists said, as pressure mounted on longtime autocratic President Omar al-Bashir to step down following months of deadly protests.

Initially sparked by rising prices and shortages, the unrest quickly turned to calls for al-Bashir to resign after two decades in power. A heavy security crackdown has killed scores since the current wave of demonstrations began in December, the most serious protests against al-Bashir.

Many students, doctors, markets, public transportation and other professionals were on strike Tuesday in support of al-Bashir's ouster, according to photos and videos provided by activists and posted by the Sudanese Professionals Association. The association is an umbrella group of independent professional unions that has been spearheading the recent wave of protests.

Sarah Abdel-Jaleel, a spokeswoman of the group, said in a video posted late Monday that the strike is part of their "peaceful resistance" against the government.

The country's intelligence and security officials, along with al-Bashir, insist that the rallies are the work of what they describe as "evil" foreign powers, and have vowed to stop them.

Al-Bashir has banned unauthorized public gatherings and granted sweeping powers to the police since imposing a state of emergency last month, and security forces have used tear gas, rubber bullets, live ammunition and batons against demonstrators.

Activists say at least 57 people have been killed in the current wave of protests, but the government total stands at 30, including police. The figures have not been updated in weeks.

Opposition leaders, doctors, journalists, lawyers and students have been arrested, along with some 800 protesters. Emergency laws and night-time curfews have been imposed in some cities.

Al-Bashir's current term ends in 2020, and he would not be able to seek another term without amending the constitution.

Though he has repeatedly promised not to run again, a parliamentary committee was tasked with amending the constitution to scrap presidential term limits. In February, the committee cancelled its meetings in what appeared to be the only political concession by al-Bashir so far.