China, North Korea's most important ally, yesterday joined other world powers in calling for a tough response to the reclusive communist state's announcement of a nuclear weapons test.

China and Russia, which both border North Korea, met with other veto-holding members of the UN Security Council to discuss a range of sanctions proposed by the United States and Japan to pressure Pyongyang to abandon its nuclear programme.

China's UN Ambassador, Wang Guangya, told reporters: "I think that there has to be some punitive actions." He added: "We need to have a firm, constructive, appropriate but prudent response to North Korea's nuclear threat."

In Moscow, Russian Defence Minister Sergei Ivanov called the reported test a "colossal blow" to the non-proliferation regime but, like China, insisted an eventual United Nations resolution on this issue should not involve the use of force.

"For us that is very important... imagine if there was military action on the territory of North Korea... North Korea has borders with three countries, and one of them is Russia," he told reporters.

The US, France and Britain, the other Council permanent members, agreed that tough measures were needed fast, despite the fact that only one country - Russia - has said the evidence so far available confirms a nuclear blast actually occurred.