WASHINGTON/SEOUL (REUTERS) - The USS Abraham Lincoln carrier strike group is operating in waters off the Korean peninsula, a United States official said, after South Korean media reported that the ships were deployed amid tensions over North Korea's missile tests.

The official said the group is in the Sea of Japan, also known as the East Sea, for exercises with Japanese forces to reassure allies and partners in the region. The move comes as United States officials are increasingly concerned that North Korea could carry out an underground nuclear test in the coming days.

This is the first time since 2017 that an aircraft carrier group has deployed to the waters between South Korea and Japan. That year, the USS Ronald Reagan, USS Theodore Roosevelt and USS Nimitz, as well as their multi-ship strike groups, deployed in a show of force over North Korea's missile and nuclear weapon tests.

South Korea's Yonhap news agency cited unnamed informed sources who said the USS Abraham Lincoln would be operating in the area for three to five days.

Responding to South Korean media reports on Monday (April 11), a spokesman for US Forces Korea said it would not comment on planned or ongoing drills.

Advisers to South Korean President-elect Yoon Suk-yeol sought redeployment of US strategic assets, such as aircraft carriers, nuclear bombers and submarines, to the Korean peninsula during talks held on a visit to Washington last week.

South Korea's Defence Ministry said it is aware that the carrier group is in international waters but declined to comment on the reports, because it is a US military asset.

North Korea has previously criticised US military drills as a rehearsal for war, and said they increase tensions.