MINNEAPOLIS (REUTERS) - The US Department of Justice said on Thursday (May 28) it had made its investigation into police involvement in the death of Mr George Floyd a "top priority," after a second day of protests in Minneapolis over the unarmed black man's death.

Experienced prosecutors and investigators from the Federal Bureau of Investigation had been assigned as part of a "robust" probe into whether the police officers involved had violated federal laws, the department said in a statement.

The statement followed a second day of protests in Minneapolis triggered by rage over the death of Mr Floyd, a black man who was seen in a widely circulated video gasping for breath as a white officer knelt on his neck.

Mr Floyd, 46, died on Monday. The investigation will be carried out by the US Attorney's Office for the District of Minnesota, the Justice Department's civil rights division and the FBI's Minneapolis Field Office.

The widely circulated video of Mr Floyd's fatal encounter on Monday night with the police, taken by a bystander, showed him lying face down and handcuffed, groaning for help and repeatedly saying, "please, I can't breathe," before becoming motionless.

A second day of demonstrations, began on Wednesday hours after Minneapolis Mayor Jacob Frey urged prosecutors to file criminal charges against the white policeman shown pinning Floyd to the street. Police fired tear gas and rubber bullets as people set buildings on fire and looted stores.

The victim's brother Philonise Floyd told CNN on Thursday that he was "tired of seeing black men die" and understood people's anger but urged protesters to be peaceful.

"To the police, I want them to get everything right, start doing your job the right way because I haven't been seeing it," Mr Philonise Floyd said.

"I want justice, I just want justice," he added, struggling to fight back tears.