A US Apache helicopter pilot has been killed and another injured in a training accident northwest of Kuwait, the US military said. 

"One AH-64 Apache pilot was killed and another injured in a training accident that occurred northwest of Kuwait City" on Friday, a statement said on Saturday. 

The injured pilot was evacuated to a US military hospital and is in a stable condition, the statement added. 

The names of the pilots and their unit were withheld pending the notification of the next of kin. The unit is currently in Kuwait as part of 'Operation Iraqi Freedom', the statement said. An investigation has been ordered into the incident. 

Some 25,000 US troops are stationed in Kuwait, which served as a launch pad for the US-led invasion of Iraq that toppled Saddam Hussein in April 2003. The emirate is also used as a transit point for US-led forces going in and out of Iraq. 

Three US soldiers were killed in Kuwait last month in a hit-and-run traffic accident.