N Korea sets rocket launch date
North Korea has said it plans to carry out a controversial rocket launch between 4 and 8 April.
The International Maritime Organization said it had received a communication from Pyongyang confirming the launch.
South Korea and the US say Pyongyang may be preparing to test-fire a long-range missile and have warned it not to go ahead with the launch.
But North Korea insists it is preparing to send up a communications satellite, not a missile.
It has said any attempt to shoot it down will result in war.
North Korea's neighbours believe it is planning to test-fire the Taepodong 2 missile - which is capable of reaching Alaska - from the Musudan-ri base in Hwadae on its north-east coast.
It first tested the missile in July 2006, but it failed less than a minute after launch.
Earlier this month Japan suggested it could deploy a vessel equipped with missile interceptor technology to the Sea of Japan (East Sea) to shoot the rocket down.
On Thursday, it called on North Korea to exercise restraint, saying it "would not tolerate" its moves to raise tensions in the region.
The IMO said Pyongyang informed the agency of its intentions on Wednesday - confirming earlier reports by South Korean officials.
North Korea's missile programme
"We have received a letter and it contains dates, times and coordinates," said IMO spokesman Lee Adamson, confirming the dates as 4-8 April.
The BBC's John Sudworth in Seoul says guidelines state that the world transport authorities should be informed in advance, so they can warn ships and planes.
A South Korean maritime ministry official, citing information from the IMO, said the North referred to areas in the Pacific Ocean and the Sea of Japan (East Sea).
The ministry said the rocket's booster would fall into the sea between Japan and the Korean peninsula, and its main body would plunge into the Pacific.
Our correspondent says that despite a range of international sanctions, North Korea has built what it calls "an experimental communications satellite" and a rocket capable of delivering it into orbit.
If successful, the launch would have a major propaganda message - North Korea would have beaten its Southern rival into space, our correspondent says.
South Korea's own home-grown satellite project is not scheduled for take-off until later in the year.
The reports come a day after US Secretary of State Hillary Clinton warned that Washington had "a range of options" it could take if North Korea went ahead with the launch - including, Reuters reported, action in the UN Security Council.
She said the six-way talks on ending North Korea's nuclear programme would not be affected.
Mrs Clinton also expressed disappointment that a US special envoy who had just visited the region was not invited to Pyongyang.
North Korea's move is stoking already heightened tensions with South Korea.
Pyongyang said it had put its military on full combat alert as an annual military exercise by US and South Korean forces began earlier this week.
And in January, the North scrapped a series of peace agreements with the South over Seoul's decision to link bilateral aid to progress on denuclearisation.
North Korea's reported move comes at a time of raised tensions with Seoul