South Korea's top nuclear envoy began full-fledged consultations Wednesday with his American and Japanese counterparts on ways to deal with North Korea's claimed nuclear test.

Hwang Joon-kook, special representative for Korean Peninsula peace and security affairs, had phone talks with his U.S. counterpart Sung Kim, according to the Foreign Ministry.

They compared notes on the initial assessment of the current situation and discussed future steps through the U.N. Security Council, it said.

The 15-member council is set to hold an extraordinary session in New York to touch on the North's claim that it has "completely succeeded" in a hydrogen bomb test.

It appears certain that the North conducted its fourth-known nuclear test earlier Wednesday, while South Korean military officials says the tremor of the artificial quake is too weak to regard it as based on hydrogen.

Hwang also telephoned Japan's nuclear envoy Kimihiro Ishikane. He requested Tokyo take an active role in punishing Pyongyang.

Japan is a member of the U.N. council, said the ministry.

Hwang then met with Russian Ambassador to South Korea Alexander Timonin, who was quoted as saying that Moscow is taking the situation seriously. (Yonhap)