Three people, including a suspected gunman, have died following a shooting at a courthouse in the US state of Michigan.

Two court bailiffs were among those killed in the incident at Berrien County Courthouse in St Joseph.

A deputy sheriff was also injured in the shooting, the Washington Post reports. Several civilians are also reported to be injured, although it is not known if they were shot.

Governor Rick Snyder said Michigan State Police are starting an investigation into the incident.

MSP has secured the scene at the Berrien County courthouse and started its investigation into the shooting that occurred this afternoon.

— Governor Rick Snyder (@onetoughnerd) July 11, 2016

At a news conference, Sheriff L Paul Bailey said: “We don’t have all the details as to what happened or whatever occurred or how he got the weapon."

Presumptive Republican presidential candidate Donald Trump said his "thoughts and prayers" are with the victims and their families.

Thoughts and prayers with the victims, and their families- along with everyone at the Berrien County Courthouse in St. Joseph, Michigan.

— Donald J. Trump (@realDonaldTrump) July 11, 2016