Ten US sailors were missing after a US destroyer collided with an oil tanker in southeast Asia, the second serious accident involving American Navy ships in the region in little more than two months.
Returning to the White House on Sunday night, President Donald Trump responded to reporters' questions about the accident by saying: "That's too bad."
Strongly criticised on social media for his response, he later tweeted: "Thoughts & prayers are w/ our @USNavy sailors aboard the #USSJohnSMcCain where search & rescue efforts are underway."
Search and rescue efforts were launched after the USS John S McCain was involved in a collision with the Alnic MC east of Singapore and the Strait of Malacca, the US 7th Fleet said in a statement.
The collision with the tanker happened at 5.24am local time as the guided-missile destroyer was heading to Singapore for a routine visit.
"There are currently 10 sailors missing and five injured," the Japan-based 7th Fleet said.
Four of the injured were airlifted to a Singapore hospital for non-life threatening injuries. The fifth injured sailor did not require further medical attention.
"Our first priority is determining the safety of the ship and crew," Adm. John Richardson, chief of naval operations, wrote on Twitter. "As more information is learned, we will share it."
In addition to US Navy aircraft, Singaporean ships, helicopters and tug boats were in the area to help conduct search and rescue efforts after the warship suffered damage the port side aft, or left rear.
"The extent of damage and personnel injuries is being determined," it said, adding that the incident was being investigated.
Malaysia's navy chief Ahmad Kamarulzaman Ahmad Badaruddin tweeted that two ships as well as aircraft from its navy and air force had also been deployed to help look for the missing US sailors.
The destroyer was currently sailing under its own power and heading to port.
Senator John McCain, a war hero who is now being treated for brain cancer, tweeted: "Cindy & I are keeping America's sailors aboard the USS John S McCain in our prayers tonight - appreciate the work of search & rescue crews."
The vessel was named in honour of the senator's grandfather and father, who were US admirals.
Based at the fleet's homeport of Yokosuka, Japan, the USS John S McCain has a crew of 23 officers, 24 chief petty officers and 291 enlisted sailors, according the Navy's website.
The ship it hit, the Liberian-flagged Alnic MC, is a 183 metre long oil tanker with a deadweight of more than 50,000 tonnes, according to the Marine Traffic website.
The vessel was carrying nearly 12,000 tonnes of fuel oil, but there was no oil spill, a crew member said.
"We are carrying 11,987 tonnes of fuel oil. There is no oil spill. We were carrying fuel oil from Taiwan to discharge to Singapore ... We are proceeding to Raffles Reserved Anchorage where the owners will investigate the matter. There was some damage to the valve," the crew member who did not want to be identified, told Reuters via telephone.
The Maritime and Port Authority of Singapore (MPA) lists the Raffles Reserved Anchorage to the South of Bukom Island to be reserved for "vessels requiring emergency repairs and damaged vessels or as directed by the Port Master."
The MPA said no oil pollution had been reported and traffic in the busy Strait was not affected. No injuries were reported from the Alnic, it said.
A family assistance centre has been established to help family members of sailors on board the USS McCain.
The waterways around Singapore are some of the busiest and most important in the world, carrying around a quarter of the world's trade in goods and oil.
The accident comes two months after seven US sailors died when a US destroyer collided with a merchant ship off the Japanese coast.
The sailors, aged 19 to 37, were found by divers in flooded sleeping berths a day after the collision tore a huge gash in the side of the Fitzgerald.
The Fitzgerald's captain was relieved of command and other sailors would be punished after the Navy found poor seamanship and flaws in keeping watch contributed to the collision, the Navy announced last week.
An investigation into how and why the Fitzgerald collided with the other ship was not finished, but enough details were known to take those actions, the Navy said.
Euan Graham, director of the international security programme at the Lowy Institute in Sydney, called the latest accident "extraordinary" and said it would certainly lead to the asking of pointed questions within the Navy.
The incident also could affect the 7th Fleet and its readiness, Mr Graham said, according to the Washington Post.
"They were already stretched after the Fitzgerald collision, and now they've lost a second frontline destroyer at an acute time in the region, with the tensions around North Korea and in the South China Sea," he said.
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 US Navy would need to bring forward other ships to maintain its strength, a spokesman for the Seventh Fleet told Reuters it was "way too early to know".