North Korea on Sunday blasted recent combined air drills conducted by South Korea, the United States and Japan, saying such joint military actions are "the main danger factors heightening the level of the military tension" on the Korean Peninsula and its surrounding region.

South Korea, Japan and the United States conducted a joint air drill on Friday involving a U.S. B-52 strategic bomber and fighter jets of the three allies over international waters, the South's defence ministry said.

Russia's foreign minister Saturday warned the U.S., South Korea and Japan against forming a security partnership targeting North Korea as he visited his country's ally for talks on further solidifying their booming military and other cooperation.

SEOUL (Reuters) -South Korea, Japan and the United States conducted a joint air drill on Friday involving a U.S. B-52 strategic bomber and fighter jets of the two U.S. allies over international waters, Yonhap news reported, citing the South's defence ministry.