Protesters threw rocks at police in Salt Lake City after officers shot a black teenager who was attacking a man late on Saturday, authorities said.

Relatives of the teenager identified him as Abdi Mohamed, 17, and told the local Fox 13 television news channel he was in a coma at a hospital after being shot three times. Police told Reuters he was in critical condition.

The Salt Lake City Police Department said he was shot after officers in the downtown Rio Grande area saw two people attacking a male victim with metal objects and ordered the pair to drop their weapons.

"One of the males complied and dropped the weapon, the other continued to advance on the victim and was shot by officers," the department said in a statement on Sunday.