Police said they were on the scene on Sunday after a "mass shooting incident" overnight in the U.S. city of Baltimore, with CNN reporting that two people had been killed and 28 people were injured.

The city's police department said the shooting took place in the 800 block of Gretna Avenue in Baltimore but did not confirm casualties or give other information.

Bank worker kills five co-workers in Louisville, Kentucky shooting

CNN, citing officials, said nine people were found with gunshot wounds and transported to area hospitals and three of them were in critical condition.

Hundreds of people were gathered in the area for an event called "Brooklyn Day," a witness told TV station Fox 45, adding that they had heard 20 to 30 shots fired.