SEOUL — North Korea said on Friday it had tested a long-range weapon, a claim that was likely to raise tensions on the peninsula and contradicted accounts from the South and in the US that Pyongyang had fired short-range missiles.

The state-run Korean Central News Agency said leader Kim Jong Un had overseen Thursday's weapons test, the second in less than a week amid tensions with the US over their fitful drive to reach an agreement under which North Korea would give up its nuclear weapons in exchange for sanctions relief.

"At the command post, Supreme Leader Kim Jong Un learned about a plan of the strike drill of various long-range strike means and gave an order of start of the drill," KCNA said, adding that the drill was successful.

KCNA did not say what kind of weapon was fired. It avoided using the words missile, rocket or projectile.

The update came amid increasingly strained ties with the US as President Donald Trump said on Thursday he thought Kim was not ready to negotiate denuclearisation.

In New York, federal authorities said a North Korean freighter had been seized on grounds of violating UN sanctions imposed over its nuclear programme.

The officials said Wise Honest -- an 18,000-ton, single hull bulk carrier -- had exported high-grade coal and brought back machinery to the country.

During an event at the White House, Trump said US authorities were looking at the latest projectile launches "very seriously."

"They were smaller missiles, short range missiles. Nobody's happy about it," Trump told reporters.

"The relationship continues. But we'll see what happens. I know they want to negotiate, they're talking about negotiating. But I don't think they are ready to negotiate."

Two Trump-Kim summits, the most recent in Vietnam in February, have produced no tangible progress toward persuading North Korea to give up its nuclear weapons.

Thursday's missile firing came after North Korea carried out a military drill and fired multiple projectiles on Saturday, with at least one believed to be a short-range missile. — AFP