Japan was planning to slap its own set of economic sanctions on North Korea after the hardline regime flatly rejected a U.N. Security Council resolution condemning its recent ballistic missile tests, Japanese media reported Monday.

Above and beyond sanctions already called for in the U.N. resolution, Tokyo was considering banning cash remittances and freezing assets held by North Korea, according to major Japanese newspapers including the business daily Nihon Keizai.

CountryWatch: North Korea

Prime Minister Junichiro Koizumi, however, said Japan would consider helping North Korea with its economic development if the communist state agreed not to fire any more missiles and returned to six-nation talks on its nuclear weapons program.

"The door is not closed," he said. "The North must return to talks as soon as possible."

Koizumi was speaking in St. Petersburg, Russia at the close of the G-8 summit where leaders of the world's industrialized nations also called on Pyongyang to reinstate a self-imposed moratorium on long-range missile tests.

Koizumi had to settle for a somewhat weaker statement than he had hoped — the G-8 did not endorse strong sanctions or measures to enforce compliance on a launch freeze.

Japan already has in place limited sanctions against North Korea that it imposed immediately after Pyongyang test fired seven missiles earlier this month, but Chief Cabinet Secretary Shinzo Abe instructed Sunday that the additional steps be taken in response to North Korea's rejection of the U.N. resolution, the reports said.

North Korea drew international condemnation this month after firing the missiles, including a long-range Taepodong-2 believed capable of reaching parts of the U.S., violating a self-imposed moratorium.

On Saturday, the U.N. Security Council unanimously passed a resolution criticizing the launches and banning all U.N. member states from dealing with North Korea on material or technology for missiles or weapons of mass destruction.

The North's U.N. ambassador promptly rejected the resolution at the Security Council and left the chamber, a breach of typical diplomatic protocol. On Sunday, the North's Foreign Ministry warned of further repercussions.

Tokyo has so far only imposed limited sanctions against North Korean in the wake of its missile tests, including barring a trade ferry from Japanese ports.

Japan would carefully consider when to impose the additional sanctions that could be contingent on whether Pyongyang moves to test more missiles, the Nihon Keizai said.

Japan also plans to ask other countries to take similar measures against North Korea, Kyodo News agency reported.