Tokyo has begun deploying a surface-to-air missile defence system and is putting its armed forces on standby ahead of a planned North Korean missile launch this month, reports and officials said Monday.

Public broadcaster NHK reported that a naval vessel carrying PAC-3 (Patriot Advanced Capability-3) ballistic missiles left a western Japan naval base on Monday, headed for the country's southern Okinawa island chain.

Defence Minister Satoshi Morimoto on Saturday ordered the military to prepare for the rocket launch, with a defence ministry spokesman telling AFP that "our ground, marine, and air forces are now preparing to deploy troops in Okinawa", which the rocket may fly over.

Tokyo is also planning to deploy Aegis warships in neighbouring waters, the top-selling Yomiuri Shimbun and other Japanese media reported Monday.

Officials are preparing to issue an advance order as soon as Friday to shoot down the rocket if it looks set to fall on Japanese territory, after an emergency meeting chaired by Prime Minister Yoshihiko Noda, the Nikkei business daily reported.

Noda on Monday called for close cooperation with the United States, China, South Korea and Russia in preparation for the planned launch, which has drawn international condemnation.

"I have ordered cabinet ministers to gather and analyse information closely with each other and as we closely collaborate with related countries," Noda was quoted by Dow Jones Newswires as saying.

The communist North announced on Saturday that it would launch a rocket between December 10 and 22 -- its second long-range rocket launch this year after a much-hyped but botched attempt in April.

It has reportedly notified neighbours including Japan of the trajectory of the planned launch.

Washington and Seoul urged Pyongyang to scrap the launch while Tokyo reportedly postponed talks due this week with North Korea.

In April, Japan ordered missile-defence preparations, including placing one of its PAC-3 systems next to the defence ministry building in central Tokyo in response to the earlier launch.

Military preparations were also made in 2009 ahead of another North Korean rocket launch.

China, the North's main ally and key benefactor, said Sunday it was concerned at the rocket launch plans, according to state media.