"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.
It was not immediately clear why access to the mobile network had been restricted, but the measures were introduced on Friday afternoon, a day after Pyongyang's Koryo Hotel caught fire, a source with access to Koryolink said.
It was not clear if the news of the fire at the hotel had affected the service. There are more than 2.5 million mobile phone subscribers in North Korea, a country of 24 million people.
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.