At least two people were killed and 28 wounded in a mass shooting at a street party early Sunday in the US city of Baltimore, police said.

Police received multiple calls about a shooting in the city's Brooklyn neighborhood just after 12:30 am Sunday, Acting Police Commissioner Rich Worley told a press conference.

"Upon officers' arrival we located multiple victims suffering from gunshot wounds," Worley said.

One 18-year-old woman was found dead at the scene in the East Coast port city, and a 20-year-old man died after being taken to hospital, a police statement said.

The wounded were being treated at area hospitals, he added, with three of them in critical condition.

Worley said authorities were working to identify a suspect and determine a motive for the shooting.

"This is an extensive crime scene, our detectives are going to be here quite a while," he said.

Baltimore Mayor Brandon Scott, speaking to reporters at the crime scene, condemned the shooting.

"This is an absolute tragedy that did not have to happen," he said.

"It again highlights the impacts and the need to deal with the over-proliferation of illegal guns on our streets and the ability for those who should not have them to get their hands on them," Scott said.

"We will not stop until we find those cowards who decided to just shoot dozens of people, causing two people to lose their lives," he said.