South Korea says it believes it will be consulted by the US before any possible pre-emptive American strike against Pyongyang, where foreign journalists are now gathered for "a big and important event".

With a US aircraft carrier group steaming to the area, tensions on the Korean Peninsula are high amid concern that the reclusive North could soon conduct its sixth nuclear test or more missile launches in defiance of United Nations sanctions.

China, North Korea's sole major ally and benefactor, has called for a peaceful resolution after a sharp rise in rhetoric between the United States and Pyongyang.

While US President Donald Trump has put North Korea "clearly on notice" that he would not tolerate provocative actions by the North, US officials have said his Administration was focusing its strategy on tougher economic sanctions.

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Trump has diverted the USS Carl Vinson aircraft carrier group towards the Korean Peninsula, which could take more than a week to arrive, in a show of force aimed at deterring North Korea from conducting another nuclear test or launching more missiles to coincide with major commemorative events.

The possibility of US military action against North Korea in response to such tests gained traction after the US Navy fired 59 Tomahawk missiles at a Syrian airfield last week in response to a deadly gas attack.

South Korean Foreign Minister Yun Byung Se said he believed Washington would consult Seoul if it was considering a pre-emptive strike against the North.

"Under the South Korea-US alliance, any important measure on the North is taken under consultation with the South Korea Government and it will continue in the future," Yun told a parliamentary hearing.

A Washington-based think-tank that monitors North Korea, 38 North, said satellite images taken today showed continued activity around the North's Punggye-ri nuclear test site on the east coast that showed it was ready for a new test.

South Korean officials say there are no new signs to indicate a North Korean nuclear test was more likely, although they also said the North has maintained a state of readiness to conduct such a test at any time.

North Korea marks the 105th anniversary of the birth of state founder Kim Il Sung on Saturday. In 2012, it tried but failed to launch a long-range rocket carrying a satellite to mark the date and tested a newly developed intermediate- range missile last year.

Around 200 foreign journalists are in Pyongyang for North Korea's biggest national day, called "Day of the Sun". Officials gave no details of the big event and similar announcements in the past have been linked to relatively low- key set pieces.

North Korea's official KCNA news agency reported that leader Kim Jong Un had guided training of the army's special operation forces jumping from aircraft to strike at targets.

"Watching the brave combatants mercilessly blow up the enemy targets, he said with pleasure that the commanding officers made correct decisions, adding those combatants carrying out their duties independently and pro-actively were reminiscent of fierce tigers crossing the mountain ranges in the southern half," KCNA reported.

North Korea has warned of a nuclear attack on the United States at any sign of American aggression.

- Reuters, AAP