South Korean Unification Minister Kwon Young-se gives a statement against North Korea at the government complex in Seoul, April 11. Yonhap

North Korea has been raising the level of threats by repeatedly holding drills simulating tactical nuclear attacks on the pretext of joint military exercises by South Korea and the United States, Seoul's unification ministry said Wednesday.

In a report submitted to a parliamentary committee session, the ministry said the North has posed a "blatant" nuclear threat to its enemies by unveiling smaller nuclear warheads and testing various weapons.

"The North has continued to maintain its confrontational stance against the South and the U.S., while deepening its ties with China and Russia," the ministry said.

North Korea remained unresponsive to an inter-Korean liaison communication channel for the sixth straight day Wednesday, without specifying any reasons.

Unification Minister Kwon Young-se voiced "strong" regret Tuesday over the North's refusal to respond to the inter-Korean communication channel, calling it a "unilateral and irresponsible" move.

The ministry said it will explore cooperation with a third country or ways to use the United Nations Command's communication channel with the North if there is a need for emergency contact with Pyongyang.

The government also said North Korea is likely to expand exchanges of personnel and trade with China and Russia.

China's new ambassador to the North, Wang Yajun, began his official activities last week, becoming the first foreign envoy to be allowed to enter the North amid COVID-19 lockdowns. (Yonhap)