U.S. Navy officials said the North Koreans lost contact with one of its submarines which is now presumed to be sunk.
The U.S. intelligence units observed North Korean vessels search for the submarine over a period of several days, CNN reported.
The reports come in the wake of one of major South Korea – U.S. Navy exercises, Ssang Yong 2016 and the arrival of the aircraft carrier USS John C. Stennis in Busan, Korea.
USNI News reported an official saying that the submarine went missing about a week ago and that North Koreans never made an attempt to indicate there was something wrong or that they needed help or assistance.
North Korea operates a fleet of around 70 submarines consisting of 20 Romeo class submarines, 40 Sango class submarines and 10 midget submarines from the country’s two submarine bases.