SEOUL-- Top diplomats of South Korea and Britain have discussed countermeasures against North Korea's sixth nuclear test, the foreign ministry here said Monday.

In a telephone conversation held Sunday night, Foreign Minister Kang Kyung-wha asked her British counterpart Boris Johnson to lend "active support" of efforts to intensify sanctions and pressure on the North "to the maximum level" so as to make it change its behavior, according to the ministry.

Johnson strongly condemned the North's latest nuclear test and expressed his full support for the Seoul government's stance regarding the situation on the Korean Peninsula. He emphasized that the U.K. will extend strong support as a permanent UNSC member for a tough resolution against the North, the ministry said.

He also promised to work together with South Korea and the United States to secure "constructive" cooperation from China and Russia to resolve the nuclear stalemate.

The Kang-Johnson conversation is part of South Korea's diplomatic drive to maintain close communication with other major countries in the face of the growing nuclear threat from the North.

Kang spoke with U.S. Secretary of State Rex Tillerson, Japanese Foreign Minister Taro Kono and her EU counterpart Federica Mogherini on Sunday via telephone to discuss cooperation, hours after Pyongyang announced the successful test of what it claimed to be a hydrogen bomb.

Source: Yonhap News Agency