Japan is to impose tough new sanctions against North Korea in response to its claimed nuclear test.
Monday's news of the claimed test has sparked global concern
The new measures will include banning all North Korean imports and stopping its ships entering Japanese waters, a government spokesman said.
Japan is also backing US-led efforts to get the UN to impose separate sanctions against the North.
The moves came as the North's second most powerful leader threatened more tests if the US remained "hostile".
The Japanese measures, announced by Chief Cabinet Secretary Yasuhisa Shiozaki, will come into effect following a formal cabinet meeting on Friday.
N KOREA NUCLEAR PROGRAMME
Believed to have 'handful' of nuclear weapons
But not thought to have any small enough to put in a missile
Could try dropping from plane, though world watching closely
They include new restrictions which will prevent almost all North Koreans from entering Japan.
"We cannot tolerate North Korea's actions if we are to protect Japanese lives and property," Prime Minister Shinzo Abe told reporters.
"These measures were taken to protect the peace."
The sanctions will be in addition to measures Japan announced in July, in response to North Korea's testing of missiles.
The BBC's Chris Hogg in Tokyo says the sanctions will hit North Korea's export of produce like clams and mushrooms, which earns precious foreign currency in Japanese markets.
Trade between the two countries was worth $180m (£97m) last year, although it has been falling for several years as political relations between the two countries deteriorated.
The moves came as North Korea's second most powerful leader threatened more tests, in the first comments from a senior North Korean official since the claimed nuclear test on Monday.
"If the United States continues to take a hostile attitude and apply pressure on us in various forms, we will have no choice but to take physical steps to deal with that," Kim Yong-nam told Japan's Kyodo news agency.
He also said North Korea would be willing to return to stalled six-party talks on its nuclear programme if existing sanctions were lifted.
France's defence minister, meanwhile, said the claimed test may have failed or was a fake.
"Given its weak power, it is hard to say if it was a very large, but traditional, type of explosion or else a nuclear explosion... If it was a nuclear explosion, it was a failed explosion," Michele Alliot-Marie said.
The UN Security Council is debating what multilateral sanctions North Korea is to face in response to the claimed nuclear test.
US SANCTIONS PROPOSAL
Halting trade in material that could be used to make weapons of mass destruction
Inspections of cargo going in and out of North Korea
The ending of financial transactions used to support nuclear proliferation
A ban on the import of luxury goods
It is due to continue discussing a draft resolution of punitive sanctions proposed by the US.
The US proposal includes halting trade in material that could be used to make weapons of mass destruction; inspections of cargo going in and out of North Korea; a ban on imports of luxury goods; and a ban on financial transactions used to support nuclear proliferation.
There is agreement in the Security Council that North Korea should face punitive measures.
The US wants the sanctions to be brought under Chapter Seven of the UN Charter, which means they would be mandatory and ultimately enforceable by military means.
But China, Russia and South Korea have expressed varying degrees of opposition to such a resolution.
The underground test reportedly took place in Gilju in Hamgyong province at 1036 (0136 GMT) on Monday morning.
Russia is the only country to have confirmed that it was a nuclear explosion.