South Korea and the United States launched their annual joint military exercises on Monday despite strong oppositions from the Democratic People's Republic of Korea (DPRK).

The drills, named as Ulchi Focus Lens (UFL), will last for 12 days.

According to South Korean Defense Ministry, about 10,000 U.S. troops, with about half of them coming from outside of the Korean Peninsula will participate in the drills.

Some 500 key players among the troops from outside Korea will be actually deployed in South Korea, with the rest to stay abroad and take part in the UFL, said a U.S. Forces Korea spokesman.

The UFL, which began in 1975, is the world's largest computerized command-and-control exercise to foster joint defense capability of South Korea and the United States.

The DPRK has strongly condemned the UFL military drills and warned the exercise will trigger a "catastrophic impact."