North Koreans are unable to access uncensored Internet, except for on rare occasions, but foreign residents and visitors to the country are able to buy 3G mobile SIM cards.
"Unfortunately we are facing internet service outage from the local internet provider's side with no estimated time, we will keep you posted once the service is back to normal," the provider, Koryolink, said in a notice sent in English to subscribers, Reuters reported.
There are more than 2.5 million mobile phone subscribers in North Korea.
Pyongyang has in the past introduced mild restrictions on the ability of foreigners to access mobile 3G Internet.
Subscriptions bought by foreign visitors usually only last for the duration of their visa.