TOKYO, Oct 5: A US military plane capable of detecting radioactive particles in the air left southern Japan on Thursday amid concerns North Korea could soon test a nuclear bomb.

The WC-135C plane flew from the US Kadena airbase in Okinawa in the direction of the Korean peninsula shortly before noon, the Japanese public network NHK reported.

The Kyodo news agency also reported the departure of the plane, although neither reports confirmed its mission.

The NHK said a midair refuelling plane also took off from Kadena at the same time and was expected to accompany the WC-135C.

The WC-135C is a special purpose aircraft that can monitor nuclear tests, NHK said.

The aircraft, usually based at the Offat airbase in Nebraska, is known to be capable of collecting air particles and gases and analysing them.

The Pentagon also declined to confirm or deny the reports.

Reports of the flight came after North Korea on Tuesday dramatically raised the stakes in the long-running standoff over its nuclear programme by announcing it would test a bomb at an unspecified date.

The warning prompted Japan to call on the UN Security Council to impose tough sanctions on Pyongyang if it went ahead with a test.

The United States said it had detected possible preparations for a nuclear test and a leading South Korean newspaper predicted the communist regime could detonate a bomb as early as next week.

The plane has been seen flying in to Kadena in recent years when tensions hiked over North Korea’s nuclear arms development. It has been seen based at the base since last May, NHK said.

US forces in Japan could not immediately confirm reports of the plane’s movements.—AFP