North Korea has banned foreign runners from participating in an international marathon scheduled to be held in the capital in April, citing fears about the spread of the deadly Ebola virus, a Beijing-based travel agency said.

North Korea is thousands of kilometres from the epicentre of the Ebola outbreak in West Africa and has reported no cases of the virus, which has killed more than 9,000 people.

Nonetheless, its borders have remained closed to foreign tourists since last October, for fear the virus might spread, and it imposes a strict 21-day quarantine for foreign aid workers and diplomats, who have been told to stay in embassy compounds.

"Our North Korean partners in Pyongyang contacted us this morning with news that the 2015 Pyongyang Marathon has - as of today - been closed to amateur and professional foreign runners," Nick Bonner, director of Koryo Tours, told the Reuters news agency. 

Pyongyang, the isolated country's capital, has held an international marathon most years since 1981 but last year was the first time foreigners had been allowed to compete.

Bonner, speaking with the AP new agency, said he remains hopeful the Ebola restrictions will be lifted by the end of next month.

But he said marathon organisers were probably still concerned that the large number of foreign tourists might pose a problem considering the lingering level of worry over the spread of the virus in the North.

Despite its wariness of the outside world, North Korea has made a concerted effort to bolster its tourist trade in recent years by setting up special tourism zones and developing scenic areas and recreational facilities.

The push is aimed primarily at Chinese tourists. Tens of thousands of Chinese tourists visit each year, according to Koryo Tours, while only a few thousand go from other countries.

Source: Agencies