North Korea accuses US of 'biological warfare plot'

North Korea has accused the United States of targeting it in an anthrax attack and has urged the UN security council to investigate America's "biological warfare schemes".

A letter from Pyongyang's UN ambassador to the Security Council president and the UN chief claims the US "possesses deadly weapons of mass destruction" and is trying to use them against North Korea.

US defence officials disclosed in late May that low concentration samples of live anthrax were shipped to labs in 19 states and four countries, including a US military facility in South Korea.

The anthrax was supposed to have been killed with gamma rays before being shipped.

North Korea is highly sensitive to the US military presence in South Korea, strongly objecting to annual US-South Korean military exercises.

Ambassador Ja Song Nam's letter says the shipment of live anthrax to South Korea means the US "is attempting to use them in actual warfare" against his country.

US State Department spokesman Jeff Rathke told reporters in Washington the allegations were "ridiculous" and did not "merit a response".