North Korean tourism officials on Thursday urged Vietnamese travellers to seize a "golden" opportunity to visit the country following a summit between Kim Jong Un and US President Donald Trump in Hanoi last month.

With an economy crippled by international sanctions, North Korea is keen to boost its nascent tourism sector by attracting more foreign visitors, the bulk of whom currently come from China.

A North Korean tourism official said it is prime time for Vietnamese visitors to travel to the country after Hanoi hosted Trump and Kim for a second round of nuclear talks in February.

"We had a very successful summit in Hanoi... this is the right chance, the golden chance for us to generate a tourist market of Vietnam to DPRK," Ham Jin of the official Korea International Travel Company (KITC) told AFP Thursday.

His company hosted a booth at a tourism fair in Hanoi this week -- with brochures advertising a dolphinarium, a science and technology complex and the Victorious Fatherland Liberation War Museum in "ever-changing" Pyongyang -- while others urged skiers to pay a visit to the Masikryong mountain resort.

Kim paid an official visit to Hanoi after his meeting with Trump, piquing curiosity among some Vietnamese eager to know more about the North Korean leader and his country.

"I want to discover this mysterious country because there are many things to see," said Do Thi Phuong Thuy, who signed up for a tour after Kim's trip.

North Korea receives an estimated 100,000 foreign tourists a year, according to industry insiders, though Pyongyang does not publish visitor data.

Ham put the number at double that and said visitor numbers grew by as much as 50 percent last year, though his figures could not be verified.

"We (use) tourism to contribute to economic development," he told AFP.

A Vietnamese tour operator at the fair said his client numbers have surged this year, but that some travellers remain wary.

"People are concerned North Korea isn't safe or is closed to the world... there are the difficulties for us when we promote tours to North Korea," Nguyen Cong Hoan, director of Hanoi Red Tours, told AFP.

Trump has heralded North Korea's economic potential, praising its "great beaches" that he said would make ideal locations for condos.

North Korea is currently building a sprawling seaside resort known as the Wonsan-Kalma Coastal Tourist Area in a zone that has previously been used for artillery drills and ballistic missile launches.