American tourist Nicholas Burkhead said he'd be happy to return to his latest holiday destination, with its beautiful scenery, great food and friendly people.

The problem is, the destination was North Korea and a US State Department ban on travel to the isolated country takes effect on Friday.

Burkhead, a 35-year-old from Tulsa, Oklahoma, was among the last American tourists to leave North Korea, landing on Thursday in Beijing.

"I was surprised at how friendly everyone was," Burkhead said after stepping off the last scheduled flight to Beijing from the North Korean capital, Pyongyang, before the US travel ban kicks in.

"It was very relaxing - beautiful scenery and they fed us very well in the restaurants there, but the exchange rate wasn't too good for the local won," he told a waiting scrum of reporters.

Burkhead arrived in Beijing on North Korea's state-owned Air Koryo after visiting Pyongyang as well as the city of Kaesong near the heavily armed border with South Korea. His five-day tour cost 1,850 euros ($2,200).

Other Americans on the flight included two aid workers as well as Jamie Banfill, 32, who had led tours to North Korea but was visiting this time as a tourist.

Banfill, who had made the trip to say goodbyes after regularly travelling to the North for a decade, said the travel ban short-sighted.

"It's an extremely complex situation on the Korean peninsula and they oversimplified it," he said.

The United States last month announced a ban on US.passport holders from travelling to North Korea, effective September 1. Journalists and humanitarian workers are allowed to apply for exemptions under the ban, which is similar to previous US restrictions on travel to Iraq and Libya.

Heidi Linton, director of Christian Friends of Korea, who has been working in North Korea for more than 20 years, told reporters she worried about the people her aid group helped, if her exemption was not granted soon.

"We started a hepatitis B program and we have 705 patients that have been started on life-saving medicine, that if they go off that medicine then their lives are in danger," she said.

It was not immediately clear how many Americans had sought, or been granted, exemptions or how many were still in North Korea. An official at the state department said it was not able to give an estimate on the number of US citizens there.

PRESSURE GROWS

North Korea is under growing international pressure over its nuclear tests and repeated ballistic missile launches, including one this week that flew over northern Japan.

The US ban on travel to North Korea followed the death of US college student Otto Warmbier, who was jailed during a tour last year.

Warmbier, who was sentenced to 15 years hard labour for trying to steal a propaganda sign, was returned to the United States in a coma in June and died six days later. The circumstances surrounding his death are not clear, including why he fell into a coma.

Warmbier had been detained leaving the airport in Pyongyang.

"I was expecting a strict security check on exit but there was nothing like that," Burkhead said.

The State Department declared US passports invalid for travel to, in or through North Korea. The restriction applies for one year unless extended or revoked by the secretary of state.

North Korean state media has described the ban as a "sordid" attempt to limit human exchanges.

North Korea is currently holding two Korean-American academics and a missionary, as well as three South Korean nationals who were doing missionary work.

This month, North Korea released a Canadian pastor who had been imprisoned there for more than two years.

Hundreds of Americans are among the 4,000 to 5,000 Western tourists who visit North Korea annually, according to US lawmaker Joe Wilson.