After reviving the huge performances known as Mass Games last year to sell an image of international engagement and peace, North Korea will again host the event this year, foreign tour agencies said.

Last September's Mass Games were the first in five years and part of a carefully choreographed weekend of events designed to highlight North Korean leader Kim Jong Un's diplomatic campaign and plans for economic development.

Koryo Tours, one of several agencies that offered tours to the games last year, said on its website on Thursday that the event would be held again, likely in September but possibly stretching to other months as well.

"The Mass Games are an art form in North Korea, developed over decades," the company said in a blog post.

"They involve up to 100,000 performers in massive synchronized displays of gymnastics and dance. There's truly nothing like it in any other country."

Young Pioneer Tours said they are also accepting bookings for the show and "expect demand to be very high."

"The revival of the event proved hugely popular, with tours to North Korea fully booked for the duration of the new incarnation of the Games," the company said of the 2018 show.

With thousands of twirling gymnasts and dancers backed by an ever-changing display of images and words glorifying the North Korean state and its people, past Mass Games have produced some of the most iconic images of the isolated country.

Unlike some past shows, last year's imagery largely avoided anti-American themes, though one part of the show compared sanctions over North Korea's nuclear weapons and ballistic missile programs to waves crashing against the country.

The event provided a chance for Kim to raise foreign currency at a time when tourism remains one of the few reliable sources of income amid tough United Nations sanctions.

The Mass Games performances are a major draw for tourists, most of whom come from China, but the inclusion of thousands of child performers has been criticized by rights groups as tantamount to forced child labor, and testimonies collected by defector groups describe harsh training regimes.