Ten sailors are missing after a U.S. warship collided with an oil tanker east of Singapore on Monday, the U.S. Navy said, the second accident involving U.S. Navy destroyers in Asian waters in little more than two months.

The guided-missile destroyer USS John S. McCain collided with the merchant vessel Alnic MC while heading to Singapore for a routine port call, the Navy said in a statement.

"Initial reports indicate John S. McCain sustained damage to her port side aft," the Navy said. "There are currently 10 sailors missing and five injured."

A search-and-rescue mission was under way involving Singaporean ships, helicopters and tug boats, as well as U.S. Navy aircraft. Malaysian authorities said the collision happened in Malaysian waters in the South China Sea and that they were assisting in the search-and-rescue operation.

The warship was currently sailing under its own power and heading to port, the Navy said, without specifying which port.

The Alnic MC is a Liberian-flagged, 183 metre-long oil or chemical tanker of 50,760 deadweight tonnes, according to shipping data in Thomson Reuters Eikon.

Shipping data showed it last sent a transponder signal at 2258 GMT Sunday and had since come to a halt 10-20 km (6-12 miles) off the east coast of the Pengerang peninsula in Johor, southern Malaysia.

An Alnic crew member contacted later by Reuters by telephone said there was no oil spill from the tanker, which was carrying almost 12,00 tonnes of fuel oil from Taiwan to discharge in Singapore.

"We have not discharged the tanker yet," said the crew member, who asked not to be identified.

"We are proceeding to Raffles Reserved Anchorage, where the owners will investigate the matter. There was some damage to the valve but no oil spill."

The waterways around Singapore are some of the busiest and most important in the world, carrying around a third of global shipping trade.

SECOND COLLISION

The collision is the second involving a U.S. guided missile destroyer in the Pacific in nine weeks.

The U.S. Navy said last week it had removed the two senior officers and the senior enlisted sailor on the USS Fitzgerald, which almost sank off the coast of Japan after it was struck by a Philippine container ship early on June 17.

That collision killed seven U.S. sailors.

The USS Fitzgerald and USS John S. McCain are both ballistic missile defence (BMD) capable ships and part of the same Japan-based destroyer squadron. The Seventh Fleet has six ships assigned to BMD patrols, with half of those out on patrol at any one time.

Asked whether the U.S. Navy would need to bring forward other ships to maintain its strength, a spokesman for the Seventh Fleet said it was "way too early to know".

The series of maritime mishaps in Asian waters comes at a tense time in the region. North Korea threatened last week to fire ballistic missiles towards the U.S. Pacific territory of Guam, ratcheting up tensions with U.S. President Donald Trump, who had threatened to unleash "fire and fury" on Pyongyang if it threatened the United States.

The U.S. Navy vessel involved in the latest collision is named for the father and grandfather of U.S. Republican Senator John McCain, who were both admirals in the United States Navy.

"Cindy & I are keeping America's sailors aboard the USS John S McCain in our prayers tonight - appreciate the work of search & rescue crews," McCain said on Twitter.

Senator McCain is a Vietnam War-era naval pilot who was shot down and held prisoner for five-and-a-half years. He is now undergoing treatment for brain cancer.