North Korea wants the United Nations Security Council to investigate America’s “biological warfare schemes.” The demand comes after the Asian country accused the United States of trying to attack it with anthrax.

North Korea informed the UN chief in a letter that the United States was trying to use weapons of mass destruction against it. The letter written to UN Secretary-General Ban Ki-moon was released to the public on Friday.

North Korea is strongly against annual joint military exercises by South Korea and the United States. The north has repeatedly expressed its discontent over the U.S. presence in South Korea.

Pyongyang's UN Ambassador Ja Song Nam demanded in the June 4 letter that the Security Council should investigate the shipment of anthrax to his country. "The United States not only possesses deadly weapons of mass destruction but also is attempting to use them in actual warfare against (North Korea)," Reuters quoted the letter.

The Pentagon earlier said that live anthrax samples, a potential biological weapon, had been accidentally sent to a number of countries like South Korea, Canada, Australia and the United Kingdom. Such samples were sent to laboratories in Washington, D.C., and 19 states in the United States as well.

The Pentagon added Japan Friday to the list of countries where live anthrax samples had been shipped by mistake. It said that the samples had been sent to a U.S. military base near Tokyo in 2005; those samples had been destroyed in 2009, according to the Pentagon.

Defense Department spokesman Colonel Steve Warren clarified that there was no anthrax, inactivated or activated, in Japan at present. Warren said that the anthrax had been believed to be inactive but tested active after having been shipped to a number of destinations. Gamma rays were supposed to destroy the anthrax before it could be shipped, The Guardian reported.

According to U.S. State Department spokesman Jeff Rathke, the allegations are so ridiculous that U.S. authorities do not even care to react to them. The UN has imposed sanctions on North Korea, which do not allow the Asian nation to carry out missile launches and nuclear tests. The country is also banned from importing luxury goods.