At least three U.S. military personnel were killed on Sunday when a Marine helicopter crashed during a training exercise off the northern coast of Australia, U.S. officials said.

The Bell Boeing V-22 Osprey was carrying 23 service members when it went down at about 9:30 a.m. near the Tiwi Islands, in the Northern Territory of Australia, officials with the Marine Rotational Force-Darwin said in a statement.

Five other service members were taken to the Royal Darwin Hospital in serious condition, the statement said.

This is a developing story. Please check back for updates.