UN Secretary General Antonio Guterres strongly condemned Monday attacks on Sudanese protesters that left at least 13 dead and scores injured.

Sudanese security forces moved in to clear a main protest camp near the army headquarters in Khartoum earlier Monday using live ammunition and teargas to disperse protesters who had been camping out near the military facility since the April ouster of long-time President Omar al-Bashir.

Guterres "condemns the use of force to disperse the protestors at the sit-in site and he is alarmed by reports that security forces have opened fire inside medical facilities," his spokesman, Stephane Dujarric said in a statement.

"The Secretary-General reminds the Transitional Military Council of its responsibility for the safety and security of the citizens of Sudan," Dujarric said. "He urges all parties to act with utmost restraint. This includes responsibility for upholding the human rights of all citizens, including the right to freedom of assembly and of expression."

Among those injured Monday was opposition negotiator Abbas Medani, according to witnesses.

“We are holding the Transitional Military Council (TMC) responsible for what happened this morning,” the Sudanese Professional Association said, urging protesters "to resist this attempt."

The umbrella association has been at the heart of the demonstrations that toppled al-Bashir.

The sit-in near the army headquarters has been the epicenter of protests demanding the TMC hand over power to a civilian government.

In early April, Sudan’s military establishment deposed al-Bashir following months of popular demonstrations against his 30-year rule.

The TMC is now overseeing a two-year transitional period during which it has pledged to hold presidential elections.

Demonstrators, however, have remained on the streets to demand the TMC relinquish power -- at the earliest possible date -- to a civilian authority.

"The Secretary-General urges the parties to pursue peaceful dialogue and to stay the course in the negotiations over the transfer of power to a civilian-led transitional authority, as required by the African Union," Dujarric said.

"The United Nations is committed to working with the African Union in support of this process and stands ready to support the Sudanese stakeholders in their efforts to build lasting peace," he added