BOSTON (Reuters) - Fifteen U.S. Senators on Thursday called on the military to identify the bodies of 21 "unknown" sailors from the U.S.S. Oklahoma who were killed during the 1941 attack on Pearl Harbor and to return the remains to their families.

In a letter to Secretary of Defense Chuck Hagel, the senators, led by Democrat Chris Murphy of Connecticut and Republican Kelly Ayotte of New Hampshire, noted that in recent years historians have succeeded in identifying the remains of other sailors who died in the battle that drew the United States into World War Two.

The remains of the 21 men are contained in five coffins at the National Memorial Cemetery of the Pacific in Hawaii, where they were buried after the battleship Oklahoma was salvaged in 1943, the senators wrote.

"The brave men who died protecting our great nation at Pearl Harbor deserve a final resting place of their families' choosing," the senators wrote. "We request that their remains be released to their family so that they may be interred according to their wishes."

About 2,400 Americans died and more than 1,000 were wounded when the Japanese launched a surprise attack on Pearl Harbor in Hawaii on December 7, 1941. The casualties included 429 crew members of the Oklahoma.

The attack sunk or badly damaged a dozen U.S. warships and destroyed 323 aircraft, crippling the United States naval operations in the Pacific Ocean.

(Reporting by Scott Malone; Editing by Jon Herskovitz adn Gunna Dickson)