At least nine people are dead and 16 reportedly injured after a gunman opened fire in the US state of Ohio, mere hours after 20 people were killed in a mass shooting in El Paso, Texas.

The shooting started around 1am on Sunday (local time) outside Ned Peppers Bar in Dayton's Oregon District neighbourhood.

Dayton Police Department confirmed the gunman was killed after officers returned gunfire.

At least sixteen people wounded in the shooting have been hospitalised. The extent of their injuries is so far unknown.

"We had officers in the immediate vicinity when this shooting began and were able to respond and put an end to it quickly," Dayton Police Department posted on Twitter.