Sudan's doctors will go on an indefinite strike in the first of a series of work stoppages amid protests calling on the country's longtime autocratic leader, President Omar Bashir, to step down, an umbrella coalition of professional unions said on Sunday.

In a statement, it said the doctors will continue to deal with emergencies during the strike, which begins Monday and aims to "paralyze" the government and deny it much-needed revenues. The coalition also called on citizens to continue their street protests, which entered their fifth day Sunday, according to activists, with demonstrations in several cities.

There have also been calls for a general strike on Wednesday, but that has not been independently confirmed.

The protests are chiefly over the rising prices and shortages of food and fuel. A steep rise decreed last week in the price of bread, a main staple for most Sudanese, proved to be the final straw. The protests prompted authorities to suspend classes in schools and universities in a string of cities, including the capital Khartoum, and to impose a nighttime curfew in some of them.

Opposition leader Sadeq al-Mahdi, whose democratically elected but ineffective government was ousted in a military coup led by Bashir in 1989, told reporters Saturday that as many as 22 people were killed in clashes with police since the protests began.

The government has acknowledged fatalities in the protests but provided no figures.

Al-Mahdi triumphantly returned home last week from a year in exile abroad. Thousands of his supporters welcomed him. Addressing a news conference Saturday, he said the protests were legitimate and that he supported a "peaceful change" of government.

Bashir, who is in his mid-70s, has in the past ordered the use of force against protesters — including in the last round of unrest in January — successfully crushing them to remain one of the longest serving leaders in the region. Although his time at the helm has seen Sudan plunging into one crisis after another, he is seeking a new term in office. Lawmakers loyal to him are already campaigning to rally support for constitutional amendments that would allow him to run in the 2020 election.

While sparked by worsening economic conditions, the ongoing protests have taken an increasingly political slant, particularly after the killing of protesters on Thursday. Demonstrators now chant slogans calling on Bashir's Islamic government to step down.

On Saturday, the ruler of the wealthy Gulf state of Qatar, Sheikh Tamim bin Hamad Al Thani, spoke to Bashir by phone, lending his support and offering aid.

"He (the emir) declared his country to be standing by Sudan and its readiness to provide all that is needed to help Sudan get through this crisis," Sudan's state news agency reported.

Qatar is at sharp odds with some of Sudan's key Arab backers, including Saudi Arabia, the United Arab Emirates and Egypt, its powerful neighbor to the north. Qatar's aid offer, the details of which are yet to be announced, could either discourage those allies from helping Bashir ride out the current crisis or, to the benefit of Sudan, prompt them to match Qatar's aid or even outdo it.

Sudan's economy has struggled to stay afloat for most of Bashir's rule, which has failed to unite or keep the peace in the religiously and ethnically diverse nation, losing three quarters of the country's oil wealth when the mainly animist and Christian south seceded in 2011. In his latest bid to secure economic aid, Bashir has strengthened ties to Gulf Arab nations, especially Saudi Arabia, sending troops to Yemen to fight alongside a Saudi-led coalition backing the government there against Iran-aligned rebels in a civil war that broke out in 2014.

He has also curbed relations with Iran, Saudi Arabia's regional archrival, to win the goodwill of Riyadh and mended ties to Egypt after a period of tension mostly because of a long-running border dispute.