Two U.S. B-1B bombers, left, are escorted by two South Korean F-15K and two Japanese F-2 fighter jets, respectively, during combined drills conducted over waters in South Korea, in this photo provided by the U.S. 7th Air Force, Jan. 15. Yonhap

North Korea warned Friday it will "more intensively" exercise the right to self-defense, denouncing South Korea, the United States and Japan for staging combined air drills, involving U.S. B-1B bombers.

The North's foreign ministry issued the statement as the three countries held joint trilateral air drills, involving two U.S. B-1B bombers, Wednesday over the Korean Peninsula following North Korea's recent launches of hypersonic and short-range ballistic missiles.

The chief of the ministry's external policy office expressed "serious" concern that "provocations" by the U.S. and its allies were adding security instability to the peninsula, according to the Korean Central News Agency.

The ministry "clarifies once again that the DPRK's exercise of the right to self-defense to defend the sovereign rights and security interests of the state will be conducted more intensively," the official said, using the acronym of North Korea's official name, the Democratic People's Republic of Korea.

The official warned his country will exercise "more thoroughly and perfectly" the right to self-defense in line with its "toughest counteraction strategy" in a bid to strongly deter any military provocations by its enemies.

The latest trilateral exercise was aimed at enhancing joint capabilities among Seoul, Washington and Tokyo over Pyongyang's evolving nuclear and missile threats.

North Korea launched what it claimed to be a hypersonic intermediate-range ballistic missile Jan. 6, followed by the launch of several short-range ballistic missiles Tuesday. (Yonhap)