Security forces on Monday killed at least 7 in Sudan's capital of Khartoum during anti-coup rallies by thousands, increasing the overall number of fatalities from the crackdown on anti-coup demonstrations to 71.

Sudan's biggest civilian opposition group, the Forces for Freedom and Change, has called for two days of civil disobedience to begin on Tuesday.

Signs posted outside closed shops said "shop closed for mourning," and one of the merchants, Othman el-Sherif was among those killed.

AFP reported that pharmacies and other shops were also closed in some parts of Khartoum.

Sudan's University for Science and Technology has ceased all operations as part of the disobedience.

According to an AFP journalist, police sprayed tear gas at dozens of protestors putting up roadblocks on the streets of east Khartoum on Tuesday, as they do on a daily basis.

The UN Special Representative Volker Perthes decried the use of live bullets, and the US embassy criticized "violent tactics of Sudanese security forces,"

Assistant Secretary of State Molly Phee and Special Envoy for the Horn of Africa David Satterfield were due in Khartoum to "reiterate our call for security forces to end violence and respect freedom of expression and peaceful assembly," according to spokesman Ned Price.

Sudan's police stated on Monday that they used "the least force" to quell the protesters, in which some 50 police officers were injured in clashes. Last week, one officer was killed.

Authorities have usually denied deploying live fire against protestors, reporting hundreds of security officer injuries since the October 25 coup. 

After virtually attending the "Friends of Sudan" talks in Saudi Arabia on Tuesday, Perthes tweeted "Deep concern about yesterday's violence. International support and leverage is needed. Support for political process needs to go along with active support to stop violence."

Sudan's Forces for Freedom and Change calls for mass civil disobedience

Yesterday, on Monday, the Sudanese opposition Forces for Freedom and Change launched a call to start a comprehensive two-day civil disobedience, starting today Tuesday, in response to "the deaths of demonstrators."

In a statement on their unofficial page on Twitter, the forces indicated that the goal of civil disobedience is to gather and unify the revolutionary forces and prepare for what they described as the decisive battle to overthrow the coup authority.

The Forces of Freedom and Change issued a previous statement, yesterday, Sunday, on the United Nations initiative on Sudan, stressing "its readiness to consult with other sectors of the Sudanese forces to restore the democratic path."