OSAN AIR BASE, SOUTH KOREA (AFP) - Four US F-22 stealth fighters flew across South Korea on Wednesday (Feb 17) to an air base near Seoul where they are being deployed in a show of force following Pyongyang's nuclear and missile tests.

Escorted by eight other US and South Korean fighter jets, the radar-evading aircraft landed at Osan Air Base near Pyeongtaek City, 70km south of the border with North Korea.

After leaving their home base in Japan's southern prefecture of Okinawa, it remains unclear how long the F-22 Raptors will stay in South Korea, which usually does not host any aircraft of that type.

Last month, a US heavy bomber flew over South Korea in the first military muscle flexing in response to North Korea's fourth nuclear test a few days earlier.

The B-52 Stratofortress at that time conducted a low-level flight before heading back to Andersen Air Base in Guam, where it is stationed.

On Monday, the USS North Carolina attack submarine arrived at the southern port of Busan for joint training with the South Korean navy.

A nuclear-powered aircraft carrier, USS John C. Stennis, is also scheduled to join the annual South Korea-US military exercise slated to open in March, Yonhap news agency said.

North Korea followed its latest nuclear test with a long-range rocket launch on Feb 7 that was widely condemned as a ballistic missile test banned under UN resolutions.