North Korea's Kim oversees air drills

North Korean leader Kim Jong Un supervised drills by its air force and underscored the need for a step-up in war preparation, state media KCNA said on Saturday.

Kim, who inspected anti-aircraft combat and air strike drills by North Korea's 1st Air Division on Thursday, called for "all units in the entire military" to bring about "a breakthrough in war preparation", KCNA said.

During May alone, Kim oversaw a missile test, inspected tank and munitions plants, made a rare visit to the Russian embassy in Pyongyang, reaffirming the country's alliance with Russia, and supervised tank firing drills and special operations unit training.

North Korea also slammed the U.S. State Department for placing it on a list of countries that do not fully cooperate with U.S. counterterrorism efforts.

North Korea has been placed on the list every year since 1997, Yonhap News Agency said.

"The more the U.S. provokes the DPRK with unnecessary and inefficient malicious acts, the further it will escalate the irreconcilable hostility between the DPRK and the U.S," its Foreign Ministry spokesperson said according to KCNA, using North Korea's official name, Democratic People's Republic of Korea.

"The DPRK will ... take effective and proper measures to cope with the U.S. hostile provocations in all spheres."