A Navy guided-missile destroyer, the USS John S. McCain, collided with a commercial vessel east of Singapore early Monday local time, the Navy said.
There were 10 sailors missing and five injured, the Navy said. "Four of the injured were medically evacuated by a Republic of Singapore navy Puma helicopter to a hospital in Singapore for non-life-threatening injuries," the U.S. Navy said in a statement. "The fifth injured sailor does not require further medical attention."
The collision, with the merchant ship Alnic MC, occurred east of the Straits of Malacca and Singapore at 6:24 a.m. Japan Standard Time, as the McCain was on its way for a routine port visit in Singapore, the Navy said.
"Initial reports indicate John S. McCain sustained damage to her port side aft," the Navy said, adding that a search and rescue mission was underway.
The ship arrived at Changi Naval Base after the collision, according to a Navy statement. "Significant damage to the hull resulted in flooding to nearby compartments, including crew berthing, machinery and communications rooms," the Navy said.
The search and rescue effort was being aided by tugboats out of Singapore, as well as the Singapore navy ship RSS Gallant, Singapore navy helicopters and a police coast guard vessel.
MV-22 Ospreys and SH-60 Seahawks from the USS America are also responding, the Navy said.
Adm. John Richardson, the chief of naval operations, tweeted, "Our first priority is determining the safety of the ship and crew. As more information is learned, we will share it."
Malaysia's navy chief, Ahmad Kamarulzaman Ahmad Badaruddin, tweeted a photo of the damaged ship on its way to Singapore after the collision and announced that the country was sending ships and aircraft to assist in the search and rescue.
The John S. McCain, which has a crew of 23 officers, 24 chief petty officers and 291 sailors, is based at the 7th Fleet's home port of Yokosuka, Japan, according the Navy's website.
Sen. John McCain tweeted that he and his wife, Cindy McCain, "are keeping America's sailors aboard the USS John S McCain in our prayers tonight - appreciate the work of search & rescue crews." The ship is named for his grandfather, John Sidney McCain Sr., and his father, John Sidney McCain Jr.
This collision comes two months after the USS Fitzgerald's collision with a Philippine-flagged container ship in the middle of the night off the coast of Japan. Seven U.S. sailors lost their lives in that collision, and last week the Navy relieved the USS Fitzgerald's commanding officer, executive officer and senior enlisted sailor for mistakes that led to the crash.
In May the USS Lake Champlain, a guided missile cruiser, collided with a fishing boat in the Sea of Japan. There were no injuries. The Navy ship tried to alert the fishing boat before the collision, but it was too late.
In February the USS Antietam, also a guided-missile cruiser, ran aground off the coast of Japan, damaging its propellers and spilling oil into the water.
ABC News' Elizabeth McLaughlin and Dean Schabner and The Associated Press contributed to this report.