Crowds gather at Pearl Harbor

Pearl Harbor survivors walk into the USS Arizona Memorial during last year's 70th anniversary of the attack on Pearl Harbor in Honolulu, Hawaii. [Photo/Agencies]

More than 2,000 people gathered at Pearl Harbor on Friday to mark the 71st anniversary of the Japanese attack that killed thousands of people and launched the United States into World War II.

Ceremonies were scheduled to start of with a moment of silence at 7:55 am, the exact time the bombing began in 1941.

The crew of a Navy guided-missile destroyer were to stand on deck while the ship passed the USS Arizona, a battleship that still lies in the harbor where it sank decades ago.

Hawaii Air National Guard aircraft were to fly overhead in missing man formation.

The US Navy and National Park Service were hosting the ceremonies, which were being held in remembrance of the 2,390 service members and 49 civilians killed in the attack.

Special recognition was given to members of the Women Airforce Service Pilots, who flew noncombat missions during World War II, and to Ray Emory, a 91-year-old Pearl Harbor survivor who has pushed to identify the remains of unknown servicemen.

Admiral Cecil Haney, commander of the US Pacific Fleet, was scheduled to give the keynote address at the ceremony. The ceremony will also include a Hawaiian blessing, songs played by the US Pacific Fleet band and a rifle salute from the US Marine Corps.

US President Barack Obama marked the day on Thursday by issuing a presidential proclamation, calling for flags to fly at half-staff on Friday and asking all Americans to observe the day of remembrance and honor military service members and veterans.

"Today, we pay solemn tribute to America's sons and daughters who made the ultimate sacrifice at Oahu," Obama said in a statement.

"As we do, let us also reaffirm that their legacy will always burn bright - whether in the memory of those who knew them, the spirit of service that guides our men and women in uniform today, or the heart of the country they kept strong and free."