Two US sailors have been shot dead and a third critically wounded at a navy base in the Gulf state of Bahrain, the US Navy has said.
The shootings took place at 0500 local time (0200 GMT) and were under investigation, the statement added.
The navy said the incident was a "domestic situation" involving female sailors and not terror-related. There was no intrusion at the base.
No explanation was given for the deaths and the sailors have not been named.
The shooting took place at a barracks at US Naval Support Activity.
The base, which is home to about 3,000 US personnel - not including crews of visiting ships - was closed for about an hour following the incident.
Bahrain is a close US ally and home to the navy's Fifth Fleet, which operates over an area of 7.5 millionsquare miles (19.4 million sq km) in and around the Gulf.
The tiny Gulf state, which consists of about 30 small islands, has been designated by Washington as a major non-Nato ally.