Riot police fired tear gas Sunday at protesters in Sudan's capital planning to march on the presidential palace, witnesses said, as backers of President Omar al-Bashir announced their own rally for next week. Deadly anti-government protests have rocked Sudanese cities including Khartoum since December 19, when unrest first broke out over a government decision to raise the price of bread.Authorities say at least 19 people including two security personnel have been killed in clashes during the demonstrations so far, but rights group Amnesty International has put the death toll at 37.On Sunday, crowds of protesters gathered in areas of downtown Khartoum after a group organising anti-government rallies called for a march on the palace.But riot police were quick to move in and disperse the protesters with tear gas, witnesses said."Police are not even allowing 10 people to gather," a witness told AFP.Video footage posted on social media networks showed protesters fleeing down streets and alleyways in the downtown area trying to escape the noxious gas.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook. The Sudanese Professionals' Association, a group of doctors, teachers and engineers, had called Saturday for the march after organising similar rallies in recent weeks."We will march on the palace on Sunday calling for President Bashir to step down," the association said in a statement.As protesters attempted the march, Sudan's Labour Minister Bahar Idris announced that a pro-government rally would be held Wednesday at Khartoum's Green Yard, a large open ground in the capital.The rally would express "the choice of the Sudanese people and address the present crisis", Idris, a former rebel from war-torn Darfur, told reporters at a press conference.Wednesday's rally would be the first pro-regime demonstration since anti-government protests erupted last month.Anti-government rallies on Sunday also broke out in the city of Madani southeast of the capital, witnesses said, with demonstrators chanting for "peace, justice, freedom".Economic crisis A separate protest was held in the northern town of Atbara, where the current unrest first erupted on December 19.Witnesses said the local market in Atbara was shut down as protesters took to the streets.Sudanese authorities have launched a crackdown on opposition leaders, activists and journalists to prevent the spread of protests that initially broke out outside of Khartoum.The country has been facing a mounting economic crisis over the past year led by an acute shortage of foreign currency.The cost of some commodities including medicines has more than doubled and inflation has hit 70 percent.Food and fuel shortages have been regularly reported across several cities, including Khartoum.