SEOUL: North Korea said it would attack U.S. military bases on Japan and the Pacific island of Guam if provoked, a day after leader Kim Jong-un oversaw a mock drone strike on South Korea.

The North also held an air raid drill on Thursday after accusing the United States of preparing a military strike using bombers that have overflown the Korean peninsula as part of drills between South Korean and U.S. forces.

North Korea has stepped up its rhetoric in response to what it calls "hostile" drills between South Korea and the United States. It has also been angered by the imposition of fresh U.N. sanctions that followed its Feb. 12 nuclear test.

Separately, South Korea said a hacking attack on the servers of local broadcasters and banks on Wednesday originated from an IP address in China, raising suspicions the intrusion came from North Korea.

"The United States is advised not to forget that our precision target tools have within their range the Anderson Air Force base on Guam where the B-52 takes off, as well as the Japanese mainland where nuclear powered submarines are deployed and the navy bases on Okinawa," the North's supreme military command spokesman was quoted as saying by the KCNA news agency.

Japan and U.S. Pacific bases are in range of Pyongyang's medium-range missiles.

It is not known if North Korea possesses drones, although a report on South Korea's Yonhap news agency last year said it had obtained 1970s-era U.S. target drones from Syria to develop into attack drones.

"The (drone) planes were assigned the flight route and time with the targets in South Korea in mind, Kim Jong-un said, adding with great satisfaction that they were proved to be able to mount (a) super-precision attack on any enemy targets," KCNA reported.

It is extremely rare for KCNA to specify the day on which Kim attended a drill. It also said a rocket defence unit had successfully shot down a target that mimicked an "enemy" Tomahawk cruise missile.

North Korea has said it has abrogated an armistice that ended the 1950-53 Korean War and threatened a nuclear attack on the United States.

Although North Korea lacks the technology to carry out such an attack, Washington said it would deploy more anti-missile batteries in Alaska to counter any threat.

PYONGYANG HAS HACKED SOUTH KOREA BEFORE

The hacking attack brought down the servers of South Korean broadcasters YTN, MBC and KBS as well as two major commercial banks, Shinhan Bank and NongHyup Bank.

South Korean communications regulators said the attack originated from an IP address based in China.

An unnamed official from South Korea's presidential office was quoted by the Yonhap news agency as saying the discovery of the Chinese IP address indicated Pyongyang was responsible.

Investigations of past hacking incidents on South Korean organisations have been traced to Pyongyang's large army of computer engineers trained to infiltrate the South's computer networks.

At least one previous attack was traced to a Chinese IP address.

South Korea's defence ministry said it was too early to blame the North but said such a cyber capability was a key part of its arsenal. Experts say thousands of North Korean engineers may have been recruited for the purpose.

"Throughout the world, states that create cyber warfare and engage in those types of activities are precisely the same countries that develop nuclear weapons," Defence Ministry spokesman Kim Min-seok said.

"North Korea has strongly stepped up development of asymmetrical strategy with nuclear development and many types of ballistic missiles as well as a special forces of 200,000 strong."