A US aircraft carrier-led strike group has set course for the western Pacific Ocean close to the Korean peninsula amid growing fears over the North’s weapons tests.

According to the US’s Pacific Command, the strike group, dubbed Carl Vinson, has set sail for the Western Pacific after departing Singapore on Saturday.

"We feel the increased presence is necessary," said an unmanned official who was speaking on condition of anonymity.

The strike group will be operating in the Western Pacific until further notice instead of partaking in a series of previously planned Australian port visits.

Last week, North Korea fired a ballistic missile into the Sea of Japan just days after it warned the global community of retaliation over sanctions.

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The test came after US President Donald Trump threatened unilateral action against Pyongyang over its missile tests.

North Korean leader Kim Jong-un looks at a rocket warhead tip after a simulated test of atmospheric re-entry of a ballistic missile, at an unidentified location in this undated file photo released by North Korea's Korean Central News Agency.

Last month, two high-ranking US intelligence officials claimed that North Korea is capable of killing millions of Americans by launching a nuclear attack.

In February, North Korea also simultaneously launched four ballistic missiles off its east coast, three of which landed close to Japan. In August, it also successfully tested a submarine-launched ballistic missile some 500 kilometers off the coast of Japan, in a move which the North's leader Kim Jong-un hailed as the "greatest success."