Small steel balls pay for a big bomb: Japan is worried that cash from pinball parlours is going to N Korea, writes Terry McCarthy in Tokyo

LITTLE steel balls, 11mm across and weighing 5.5g, are at the root of North Korea's nuclear weapons programme. Yesterday the Independent bureau in Tokyo, in the full light of day and doing nothing against the law, acquired several thousand of these balls - for 100 yen (63p).

This transaction was not performed in a private office with some shady scientific middleman flogging dual-purpose technology. It was carried out in a pachinko parlour - one of 18,000 such parlours around Japan. Distantly related to pinball machines in the West, pachinko is a national passion in Japan, taking in up to pounds 125bn a year, much of which is never declared to the tax authorities.

But while the government up to now has turned a blind eye to the activities of pachinko parlours, which operate on the fringes of anti-gambling laws, the growing concern over North Korea's nuclear ambitions has made internal security agencies take a new look at the sport that by some accounts attracts some 30 million Japanese - a quarter of the population.

The reason is that up to a third of all the pachinko parlours in the country are controlled by ethnic Koreans with links to North Korea - descendants of slave labourers brought to Japan before and during the last war. And much of the pounds 375m-pounds 500m that Koreans in Japan remit to North Korea in foreign currency every year is thought to come from pachinko. Since pachinko does not sell any tangible goods, the industry's accounts are impossible to check accurately, giving ample opportunity for North Korean sympathisers to hide substantial sums for transfer to Pyongyang. This foreign currency - often channelled through dummy companies in Macau - is vital for North Korea's acquisition of weapons technology from overseas.

Japan knows that if the current peace initiative between the two Koreas, brokered last month by former US President Jimmy Carter, does not work, then the United Nations is likely to push for economic sanctions against North Korea for its failure to comply with international nuclear inspection requirements. One of the elements in such sanctions would be putting an end to the foreign currency remittances to North Korea from Japan. The tax inspectors last month began checks on post-office accounts in Nagoya set up by pachinko parlour owners.

The players in New Aoi pachinko parlour, besides Kanda station in central Tokyo, yesterday seemed totally oblivious to the North Korean nuclear threat, as they poured money into pachinko machines. But all stood up and crowded around as Chika Miyatake, who works for the Independent in Tokyo, put a mere 100 yen worth of steel balls into a machine on a whim, and hit the jackpot.

First introduced to Japan in 1924 as a variation of a primitive American pinball game, 'Corinthian Game', pachinko quickly took root. It was named after the onomatopeic term pachi-pachi which denotes the crackling sound of the balls hitting the nails on their way down the board.

Gambling is against the law in Japan, except for a few highly regulated sports such as boat-racing or horse-racing. Technically a pachinko win entitles the player to a choice of prizes, but in fact most of these prizes are redeemable for cash at a small, anonymous window somewhere close to the pachinko parlour. The 100 yen had won 6,000 yen (pounds 37.50) in just five minutes. That at least was 6,000 yen that Kim Il Sung would not get his hands on.