Four leaders of Sudan's Democratic Unionist Party (UDP), led by Mohamed Osman al-Mirghani, presented their resignations from the legislative parliaments in protest against the government's violent conduct against peaceful demonstrators and killing them, the union said.

Mohamed Hashim, who resigned from the Legislative Council of the state of Khartoum, said his resignation came as a rejection of violence, murder and bloodshed, and blamed the government for killing the demonstrators.

Hashem added that three other deputies from his party in the Sudanese parliament submitted their resignations for the same reasons and solidarity with the Sudanese people.

Since December 19, Sudan has witnessed bloody protests following the government's decision to raise bread prices.

The protests escalated into widespread demonstrations against President Omar al-Bashir's three-decade rule that led to clashes with security forces in which several people were killed.

"We invite you to participate in the march of martyrs on 20 January in Omdurman, which will go to the parliament building and coincide with demonstrations in a number of areas of the country," the Union of Sudanese Professionals, the organization organizing the protests in Sudan, said in a statement.

Demonstrations killed and wounded (Reuters)

Memorandum of approval
The union, which includes doctors, engineers and university professors, said that "the protesters will submit to parliament a memorandum calling on Bashir to step down."

Last month, protesters staged several protests in Omdurman on the West Bank of the Nile.

Officials said at least 26 people were killed, including a security man, during a month of protests, but Amnesty International said last week the toll had exceeded 40.

Sudanese police said on Friday that only two people were killed during anti-government demonstrations in Khartoum on Thursday, while organizers of the protests said the number three.

The Union announced that it would organize night demonstrations in Khartoum on Tuesday, followed Thursday by the organization "processions to step down in the different cities of Sudan."

Analysts say the current protests pose the biggest challenge to Bashir's rule, which came to power in 1989 following a military coup backed by Islamists.

The protests come at a time when Sudan is facing a significant foreign currency shortage and rising inflation, causing more than double the price of food and medicine.