Phuket, Thailand  - Japan on Thursday announced plans to freeze the assets of five North Korean companies and five individuals, the first country to follow tougher UN Security Council sanctions on Pyongyang to halt its nuclear programme.

"Starting on July 24, the Japanese government will take measures to freeze the assets of the five entities and individuals and will ban the individuals from entering Japan," Japanese Foreign Ministry spokesman Kazua Kodama announced on the sidelines of a regional security forum on the Thai island of Phuket.

Japanese Foreign Minister Hirofumi Nakasone informed his 25 counterparts attending the Association of South-East Asian Nations (ASEAN) Regional Forum of the measure against North Korea, whose nuclear weapons ambitions are seen as the greatest security threat to the region and specifically Japan.

"This is one of the most serious issues of security in East Asia," Kodama said. "If they succeed in arming their ballistic missiles with nuclear warheads, Japan will be an easy target."

Tokyo has been pressing its ASEAN allies and the other countries attending the forum to fully back a UN Security Council resolution that imposes economic sanctions, an arms embargo and tighter security checks on North Korean cargo for illicit weapons.

"My government intends to call on other countries to join the sanctions on these companies and individuals," Kodama said, adding that Japan was believed to be the first country to fully follow through on the sanctions.

On July 16, the United Nations asked its members to freeze the assets of Namchongang Trading Co, Hong Kong Electronics, Korea Hyoksin Trading Corp, General Bureau of Atomic Energy and Korean Tangun Trading Corp as well as five North Koreans: Yun Ho-jin, director of Namchongang Trading; Ri Je-son and Hwang Suk-Hwa, both directors of separate departments in the General Bureau of Atomic Energy; RiHong-sop, former director of the Yongbyon Nuclear Research Centre; Han Yu-ro, director of the Korea Ryongaksan General Trading Corp.

The companies and directors are all connected with Pyongyang's nuclear programmes.

Japan downplayed fears expressed by US Secretary of State Hillary Rodham Clinton about the possibility of North Korea assisting Myanmar in pursuing a nuclear programme.

Myanmar Foreign Minister Nyan Win assured Nakasone Wednesday that Myanmar would comply with the UN resolution, Kodama said. (dpa)