Seoul, South Korea — Russia’s foreign minister 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.

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.

Top South Korean, US and Japanese military officers urged North Korea to cease all unlawful activities that threaten regional security, as the three nations flew advanced warplanes for a joint exercise in a show of force against the North.