North Korea's military said Friday it will take the "toughest counteraction" against the United States, with tensions rising over the North's aggression.

"Our toughest counteraction against the U.S. and its vassal forces will be taken in such a merciless manner as not to allow the aggressors to survive," the North's military said, according to the official KCNA news agency.

North Korea's military "will as ever courageously counter those who encroach upon the dignity and sovereignty of the DPRK (North Korea) and will always mercilessly foil all the provocative options of the U.S. with Korean-style toughest counteraction."

A U.S. aircraft carrier is heading for the Korean Peninsula amid growing speculation that North Korea may conduct provocative acts, including its sixth nuclear test. (Yonhap)