Ten sailors are missing and five injured after a US destroyer collided with an oil tanker off the coast of Singapore, the US Navy says.
The USS John McCain was sailing east of Singapore and preparing to stop in the port when it struck the Liberian-flagged vessel.
A wide-ranging search and rescue operation is under way.
The collision, which was reported at 5.24am local time on Monday, happened as the USS John McCain prepared to perform a routine port stop in Singapore.
Initial reports indicated that the ship had "sustained damage" to its port side, but the US Navy said it was now sailing under its own power and heading to Singapore's port.
US military helicopters as well as the Singapore navy and coast guard are conducting search and rescue efforts. Malaysia has also joined in the rescue effort.
The waterways around Singapore are among the busiest in the world, known to convey vast amounts of the world's trade in goods and oil. The Strait of Malacca itself is considered one of the most strategic commercial waterways in the world.
There are few details on the status of the oil tanker, the Alnic MC, and its crew.
Tracking website MarineTraffic put its position as several kilometres off the eastern coast of the Malaysian state of Johor on Monday morning, about 90 minutes after the incident.
The tanker has a gross tonnage of 30,000, about three times that of USS John McCain and one report suggested it was "ballasting", which means it was not loaded with oil for cargo.
US senator John McCain, whom the ship is named after, tweeted that he and his wife were praying for the sailors.
Cindy & I are keeping America's sailors aboard the USS John S McCain in our prayers tonight - appreciate the work of search & rescue crews https://t.co/jzk9giXbfg— John McCain (@SenJohnMcCain) August 21, 2017
It is the second serious collision involving a US Navy ship in recent months. In June, seven US sailors were killed when the USS Fitzgerald collided with a container ship in Japanese waters near the port city of Yokosuka.
Those who died were found in flooded berths on board the ship after the collision caused a gash under the warship's waterline.
The US Navy said last week that about a dozen sailors would be disciplined, and the commanding officer and other senior crew would be taken off the ship.
According to maritime rules, vessels are supposed to give way to ships on their starboard side.