The drills come just after the U.S. and South Korea concluded maneuvers in the Yellow Sea. The exercises brought immediate criticism from China, which is wary of having foreign navies off its shores and has been increasingly assertive over large swaths of waters in the south and east China seas, where some of the drills would take place.

“At present, there are already enough of these kinds of military exercises. Under the present conditions, all relevant parties ought to do more to benefit the maintenance of peace and stability on the Korean peninsula and in the region, and not the opposite,” said Foreign Ministry spokeswoman Jiang Yu.

The Nov. 23 North Korean attack killed two South Korean marines and two civilians on Yeonpyeong Island, a tiny enclave of civilians and military bases located near a disputed maritime border.

The attack has heightened tensions in the region and renewed fears of a bigger clash breaking out that could draw in neighboring countries, including Japan, where about 50,000 U.S. troops are based under a security pact.

The drills in and around Japan are part of the annual “Keen Sword” maneuvers and involve tens of thousands of troops from both sides, including the aircraft carrier USS George Washington and its battle group. For the first time, the exercises also have observers from South Korea.

According to Japan’s Defense Ministry, 34,100 Japanese personnel, 40 vessels and 250 aircraft from Japan’s ground, maritime and air self-defense forces will take part, along with 10,400 troops, 20 ships and 150 aircraft from the U.S. military.

The maneuvers, which were scheduled well before the North Korean incident, are to continue through Dec. 10.

“By conducting exercises such as Keen Sword, we are ensuring that our forces will continue to be effective in meeting the challenges of the 21st century,” said Lt. Gen. Hawk Carlisle, commander of the U.S. 13th Air Force.

Officials said South Korea was included for the first time since the exercises were started in 1986 in an effort to bolster cooperation between the two neighbors.

“Japan-U.S. cooperation, as well as our three-way cooperation that includes South Korea, is extremely important for peace and stability in east Asia,” Japan’s Chief of Staff Gen. Ryoichi Oriki said.

Japan has reacted with alarm to the developments on the Korean peninsula. Prime Minister Naoto Kan even ordered his Cabinet ministers to stay near the capital in case of an emergency.

North Korea’s state-run news agency has threatened “full-scale war” if the country’s territory is violated by any military maneuvers. The U.S.-Japan exercises were to be held well away from Korean territory.

Still, South Korean intelligence chief Won Sei-hoon told lawmakers this week that North Korea is likely to strike again, Yonhap news agency reported.

He said North Korea likely carried out last week’s attack in part because it needed a “breakthrough” amid internal dissatisfaction over a plan to transfer power from Kim Jong Il to his youngest son.

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Associated Press writer Christopher Bodeen in Beijing contributed to this report.