As the Security Council met to impose the sanctions, Pak Gil Yon, North Korea's ambassador to the UN, walked out of the meeting accusing members of "gangster-like" action and warning that Pyongyang considered any further US pressure a "declaration of war".

The UN resolution, which called North Korea's nuclear test a "clear threat to international peace and security", allows nations to stop cargo going to and from North Korea in order to check for weapons or related supplies.

The resolution bars trade with North Korea in dangerous weapons, imposes bans on heavy conventional weapons and luxury goods and asks nations to freeze funds connected with North Korea's non-conventional arms programmes.

The sanctions came amid continued condemnation of North Korea's test. 

Japan options

Japan's ruling party policy chief said Tokyo needed to discuss whether it should also possess nuclear weapons.

Shoichi Nakagawa, chairman of the Liberal Democratic Party (LDP) Policy Research Council, said he believed Japan would adhere to its policy of not arming itself with nuclear weapons, but added that debate over whether to go nuclear was necessary.

"China strongly urges the countries concerned to adopt a prudent and responsible attitude in this regard and refrain from taking any provocative steps that may intensify the tensions"

Wang Guangya, China's ambassador to the UN

"We need to find a way to prevent Japan from coming under attack," Nakagawa told a television programme, referring to what Tokyo should do following North Korea's reported nuclear test.

Immediately after the UN sanctions were imposed, Shinzo Abe, the Japanese prime minister, said Tokyo would consider further punitive steps against the reclusive communist state.

George Bush, the US president, said the resolution showed "the world is united in our opposition to its nuclear weapons plans".

Enforcement will depend largely on whether those who have traded with North Korea honour the bans, which now also have the support of China, the North's closest ally, as well as Russia.
  
"The key will be China sealing its border to prevent military [and] nuclear-related shipments in either direction," Ralph Cossa, the president of Hawaii-based think-tank CSIS Pacific Forum, said.

Chinese caution

Most of Pyongyang's trade crosses through China, which fears a flood of refugees if the Pyongyang government collapses.

North Korea also rests between China's border and South Korea, where 25,000 US troops are stationed.
   
China warned the 15 Security Council members not to provoke Pyongyang with "provocative steps", in particular inspections of cargo ships going to and from North Korea to check for weapons.
   
The provision was toned down at China's request, but still authorises countries to inspect cargo.

Protests have been held against
the North Korean nuclear test

Some analysts said the threat of ship inspections was an ultimatum to North Korea to respond to diplomatic overtures and return to moribund six-party talks on its nuclear programmes.
  
"The ball is in North Korea's court," said Satoshi Morimoto, professor at Takushoku University.
   
North Korea has boycotted the talks with the South, the United States, China, Japan and Russia since last year because of a US crackdown on firms it suspects of aiding Pyongyang in illicit activities such as counterfeiting.
   
But Alexander Alexeyev, the Russian deputy foreign minister, told reporters in Seoul after his visit on Friday to Pyongyang that the North has not ruled out diplomacy.