North Korea fired another ballistic missile, military officials in South Korea said, further heightening tensions in the region.

The launch comes just days after Pyongyang said it planned to mark two key anniversaries this month as "big" political events, and just days before US President Donald Trump meets China's Xi Jinping - with North Korea at the top of the agenda.

"North Korea fired an unidentified projectile in Sinpo, South Hamgyong Province, into the East Sea," South Korea's Joint Chiefs of Staff said, according to Yonhap news agency, using the local name for the sea between the Korean Peninsula and Japan.

It was not clear what kind of missile North Korea tested, but they said it had been fired from the ground, not under the water.

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The east coast port of Sinpo is home to a known North Korean submarine base.

In August last year, North Korea made a major technological breakthrough by launching a ballistic missile from a submarine near Sinpo. It flew about 480km before falling into the sea inside Japan's air defence identification zone, the area in which Tokyo controls aircraft movement. North Korean leader Kim Jong Un boasted about the launch, describing it as "the greatest success".

South Korean officials said the missile did not appear to fly very far, only about 65km. The South's national security council convened an emergency meeting.

Kim had signalled that his regime was working on a missile capable of reaching the United States, saying in his New Year's Day address that North Korea had "entered the final stage of preparation for a test-launch of an intercontinental ballistic missile". After Kim's statement, Trump tweeted: "It won't happen!"

Trump warned that the United States would take unilateral action to eliminate the nuclear threat from North Korea unless China increased pressure on Kim Jong Un's regime.

"China has great influence over North Korea. And China will either decide to help us with North Korea, or they won't," Trump said in an interview with the Financial Times this week.

Trump will host Xi for two days of talks, starting Friday, at his Mar-a-Lago resort in Florida.

This meeting, coinciding with a tense situation on the Korean Peninsula, has led to speculation of imminent provocations from North Korea.

Satellite images taken over the last 10 days have shown a prolonged and heightened level of activity at North Korea's underground testing site, sparking speculation about whether a sixth nuclear test was planned.

Plus, North Korea has resumed last year's steady firing of missiles from sites on both the east and west coasts. The last one, on March 22, exploded shortly after launch.

Regardless, nonproliferation experts say it is clear that North Korea is determined to make progress on its missile programme - and presumably on its goal to attach a nuclear warhead to a missile capable of reaching the mainland United States.

Compounding hitters, April is an important month in the North Korean calendar and the regime likes to mark important dates with fireworks - both with firework displays in the center of Pyongyang and with missile flares. The regime celebrates the 105th birthday of founding President Kim Il Sung on April 15 and the 85th anniversary of the foundation of the Korean People's Army 10 days later.