Four US F-22 stealth fighters flew across South Korea Wednesday 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, 70 kilometres (45 miles) south of the border with North Korea.

Deployment of the raptors, which are normally based on Japan's Okinawa, is the latest move by Washington to bolster defences in South Korea following North Korea's fourth nuclear test last month.

"This mission demonstrates the strength" of the US-South Korea alliance and "the resolve of both nations to maintain stability on the Korean Peninsula", Lieutenant General Terrence J. O'Shaughnessy, commander of US 7th Air Force, told journalists.

Calling the F-22 Raptor "the most capable air superiority fighter in the world" , the US maintains "an ironclad commitment" to the defence of South Korea, he added.

Last month, a US B-52 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.

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, the USS John C. Stennis, is also scheduled to join the annual South Korea-US military exercise slated for March, Yonhap news agency said.

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

- China missile concern -

The military moves come as South Korea is due to begin talks with the US this week on the possible deployment of an advanced US missile defence system which China and Russia have warned could undermine stability in East Asia.

Defence officials in Seoul and Washington say bringing the Terminal High Altitude Area Defence System (THAAD) to the South has become a clear necessity given the progress North Korea is making on its ballistic missile programme.

"This is an effort to try and put in place a defensive system that will bolster security in the region. And we think it would be an appropriate step to take at this point", US Pentagon spokesman Peter Cook said Tuesday.

China's Global Times, which has close ties to the ruling communist party, on Wednesday said editorially that if South Korea insisted on bringing THAAD to its soil, China would install more missiles in the region and take "the highest-level precautions" against the system.

"As for the US, China should be bold in expressing that the THHAD system and other military deployments around the Korean peninsula are aimed at China", the daily said.

"China should make all-round preparations, including increasing its defence expenditure and raising the number of advanced missiles so as to maintain China's deterrence".

South Korean President Park Geun-Hye on Tuesday signalled a tough new approach to derailing North Korea's nuclear weapons programme, arguing efforts to foster cooperation with the North had led nowhere.

She also called for "a fundamental solution for bringing practical change in North Korea", indicating the South would lead efforts to bring about regime change in the Stalinist state.