North korea submarine
North korea submarineReuters

A North Korean submarine has reportedly gone missing, and satellites and aircraft of the United States have reported that the country's Navy has been searching for the vessel, according to CNN. The class of the vessel is not clear yet. 

The North Korean submarine was operating along the country's east coast when it reportedly lost contact and disappeared earlier this week. Three U.S. officials told the news channel the vessel likely suffered a failure during an exercise.

It is not clear if the submarine has sunk or is adrift, but U.S. officials are speculating the former, according to the US Naval Institute (USNI) News. "The speculation is that it sank. The North Koreans have not made an attempt to indicate there is something wrong or that they require help or some type of assistance," a U.S. official told the agency. 

North Korea is believed to have a fleet of about 70 submarines. The isolated country has reportedly been working on using submarines to launch ballistic missiles and has even released purported photos of successful tests in the recent past. However, a photo released last year of a successful submarine-launched missile test was believed to be photo-shopped

In November last year,  South Korean media reported North Korea had failed in testing a missile launch from a submarine

North Korea recently threatened South Korea and the United States with nuclear strikes for participating in a joint military drill that started Monday. The U.S. reportedly deployed its aircraft carrier USS John C. Stennis (CVN-74) and a nuclear-powered submarine, as well as the B-2 stealth bomber for the exercise. The focus of this year's exercise, which was the largest between the two countries, was on improving the capability to launch strikes targeting the top leadership of the Kim Jong-un regime.