An independent union of Sudanese journalists launched a strike Thursday in support of "legitimate" popular demands for freedom and democracy, the latest in a series of work stoppages and protests calling for longtime President Omar Bashir to step down.

A union statement said the three-day strike is also a protest against authorities' "barbaric" assault on press freedoms, including censorship and confiscating newspaper editions.

Street protests have swept most of Sudan since Dec. 19, with chants evoking those of the Arab Spring in 2010 and 2011.

Amnesty International said 37 people have died in the first five days of the protests. The government has acknowledged fatalities, but gave no figures. The United States, Britain, Norway and Canada called on authorities to investigate the use of live ammunition against protesters.

An official at the journalists union said the response to the strike call was "very positive" among staff of privately-owned newspapers, but it was not clear how many employees at private television networks would join. Employees of state radio and television, as well as official newspapers, were not expected to strike, he said.

The government has heavily censored independent newspapers since the protests began, while the state media has adhered to the government line.

Reached in Khartoum, the official spoke on condition of anonymity for fear of reprisal.

An independent union of doctors started an open-ended strike on Tuesday.

In Atbara, a railway city north of Khartoum, popular neighborhood committees called for fresh protests Friday, dubbing it the "Friday of Martyrs" in memory of those killed in the latest protests.

An independent committee that monitors casualties and arrests during the demonstrations said Thursday that 19 protesters were wounded Tuesday when thousands tried to march on Bashir's Nile-side presidential palace in Khartoum. Of the 19, 10 suffered gunshot wounds, eight were hurt by rubber bullets and one suffered head wounds from a police baton, it added. It said at least 205 protesters were detained, nearly a quarter of them women.

Bashir, in his mid-70s, overthrew an elected but ineffective government when he seized power in 1989 in collaboration with Islamists. He is wanted by the International Criminal Court for committing crimes against humanity and genocide in the western Darfur region.

He has ordered the use of force against protesters in the past — 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 in power has seen one crisis after another, he plans to seek a new term in office in 2020 elections.

Sudan, a country of more than 40 million people, lost three quarters of its oil wealth when the mainly animist and Christian south seceded in 2011 after a long civil war against the Khartoum government. A currency devaluation earlier this year caused prices to surge and a liquidity crunch forced the government to limit bank withdrawals.