Pyongyang announced earlier this month that it planned to "completely" destroy the Punggye-ri facility in the country's mountainous northeast.

The demolition is due to take place sometime between Wednesday and Friday, depending on the weather, according to the North.

A handful of foreign journalists, including from South Korea, were originally invited to attend.

Reporters from China, Britain, the US and Russia on Tuesday flew from Beijing to the North Korean city of Wonsan, from where they will travel for some 20 hours up the east coast by train and bus to the remote test site.

But the South Korean press corps were left off the flight after Seoul said they had received no word from Pyongyang in recent days on whether their reporters had been accepted.

On Wednesday the Unification Ministry said Pyongyang had now granted them permission.

"The government will swiftly carry out necessary measures for the journalists such as granting approvals for visiting North Korea and providing transportation," the ministry said.

There was no word on how the South Korean reporters might reach North Korea to catch up with their colleagues.

But on Tuesday a Unification Ministry spokesman suggested the South could lay on a rare direct flight.

The peninsula has been divided ever since the end of the Korean War in 1953 and there are usually no flights between the two sides.

The North has portrayed the destruction on the Punggye-ri test site as a goodwill gesture ahead of planned June 12 summit between Kim Jong Un and Donald Trump in Singapore.

Last week Pyongyang threatened to pull out of that summit if Washington pressed for its unilateral nuclear disarmament.

On Tuesday Trump also cast doubt on talks as he met with South Korean leader Moon Jae-in.

"There are certain conditions we want to happen. I think we'll get those conditions. And if we don't, we won't have the meeting," he told reporters, without elaborating on what those conditions might be.

Punggye-ri has been the site for all six of the North's nuclear tests, the latest and by far the most powerful in September last year, which Pyongyang said was an H-bomb.

Agence France-Presse is one of a number of major media organisations not invited to cover the event.