A nuclear-powered U.S. submarine arrived in a southeastern South Korean port on Monday to participate in an annual joint military drill, a senior military official said, amid a series of provocations by North Korea.

The USS Columbus, a Los Angeles-class submarine, arrived in Busan, some 450 kilometers south of Seoul, along with the U.S. 7th Fleet command ship, the USS Blue Ridge, to participate in the Foal Eagle exercise.

The combat field training began last week and will last until April 18. Foal Eagle involves 7,500 U.S. American troops with 5,100 of them coming from abroad.

"The U.S. forces plan to jointly carry out naval drills and landing maneuvers with the South Korean Navy and Marine Corps during the Foal Eagle exercise," the military official said. "(The deployment) is part of joint deterrence measures to protect the Korean Peninsula in time of war."

The U.S. Navy confirmed the arrival of the ships, saying they are "currently in routine deployment in the West Pacific," without disclosing details of their missions.

Earlier in the day, North Korea fired two short-range Scud missiles from its eastern coast, in its latest provocation seen as a reaction to the ongoing joint military drills between the allies. Last Thursday, Pyongyang fired four Scud missiles from the same area.

The 7,000-ton submarine visited a southern naval base last year to participate in the Foal Eagle exercise. It is equipped with Tomahawk land attack missiles and Harpoon anti-surface ship missiles.

The USS Blue Ridge is the command ship of the U.S. 7th Fleet, forward deployed from Japan's Yokosuka base, and can carry over 250 officers and 1,200 enlisted sailors. (Yonhap)