TOKYO, JAPAN - Japan decided to tighten a watch on money flows to North Korea in a bid to punish the communist regime for its rocket launch, a top official said.

Tokyo also extended by a year existing sanctions -- bans on imports from North Korea and visits to Japan by its citizens and ships -- but refrained from tougher measures such as a total Japanese export ban.

The new restrictions were decided at a cabinet meeting early Friday, said the top government spokesman, Chief Cabinet Secretary Takeo Kawamura.

On April 5 Pyongyang fired a long-range rocket over Japanese territory, claiming it launched a satellite as part of a peaceful space programme.

Kawamura stressed that North Korea conducted a "missile launch," echoing the view held by Washington and Seoul that it was a thinly disguised test of an intercontinental ballistic missile.

"We assertively say this violation of the UN Security Council resolutions by North Korea is related to its ballistic missile programme," he said.

The move came as Japan struggled to secure a resolution at the UN Security Council to punish North Korea, while China and Russia have favoured a milder, non-binding statement to be read by the council president.

Japan is pushing for a "strong" statement at a summit of Asian leaders in Thailand this weekend, a diplomatic source told AFP.

The diplomat, who asked not to be named, said Tokyo had proposed a text of the statement to Thailand, which is hosting this year's summit of the Association of Southeast Asian Nations with its allies.

"We have to see how China will react," said the diplomat, noting however that Beijing had defended North Korea's right to peaceful use of space and refused to condemn its ally.

Japan's tighter watch on money is a much milder step than other options sought by some ruling-party lawmakers such as a total ban on exports to North Korea and an outright prohibition on all visits by North Korean nationals.

Critics, including some relatives of Japanese citizens abducted by North Korea in the 1970s and 1980s to train its spies, said the new sanctions didn't go far enough.

The leader of a relatives' group, Shigeo Iizuka, said that, given the regime's "insincere response to the abduction issue and the launch of a missile, (the sanctions) are still not enough," Kyodo news agency reported.

Under the new measures, which take effect next week, all remittances to North Korea over 10 million yen (100,000 dollars) will have to be reported to the government -- lowering the limit to a third of the current threshold.

The government also plans to lower the amount of cash subject to reporting by travellers to North Korea to 300,000 yen from more than one million yen.

Tokyo first imposed formal bilateral sanctions against Pyongyang in 2006, when North Korea tested missiles and a nuclear bomb.

Since then Japan has halted all imports from North Korea and visits by its citizens, except in special cases, and banned port calls by its ships, including a regular ferry service to the impoverished state.

To specifically target the leaders of the isolated Pyongyang regime, Japan has also banned exports of 24 luxury products -- including caviar, beef, fatty tuna and selected high-end consumer electronics. --AFP