North Korea says it has sent a letter to the UN Security Council rejecting an argument by South Korea that it was behind the sinking of its neighbour's navy ship and claiming it was the victim of a US-mastermined conspiracy.
The letter comes after the filing of a complaint by the South last week demanding international community action to deter further provocation by Pyongyang.
A team of international investigators led by South Korea's military said in May that a North Korean submarine torpedoed its corvette Cheonan on March 26, snapping the vessel in half in a blast and killing 46 sailors.
North Korea, through its official media, has rejected the charge saying it was a ploy by the South's President Lee Myung-bak aimed at political gains for his conservative government.
North Korea drove tensions to new heights in recent weeks by threatening war if Seoul imposed sanctions, denying any role in the sinking of the Cheonan.
The mounting antagonism between the two Koreas has unnerved financial investors, worried about armed conflict breaking out in the region.