PYONGYANG, North Korea — Warnings are appearing on Instagram accounts in North Korea that claim access to the popular photo-sharing app is being denied and the site blacklisted for harmful content.

Opening the app with mobile devices on the North Korean carrier Koryolink has resulted in a notification in English saying: “Warning! You can’t connect to this website because it’s in blacklist site.” A similar notice in Korean said the site contains harmful content, though that is not mentioned in the English version.

Such warnings have also appeared when websites that link to Instagram are accessed through desktops or laptops using LAN cables on the North Korean Internet provider. The warnings have been appearing on and off for at least five days.

Tech support staff at Koryolink said they were not aware of any changes in policy regarding Instagram. There has been no notice from the government or from the mobile phone service to its customers that Instagram has been blacklisted. Officials with Instagram had no comment when contacted by The Associated Press. Instagram is owned by Facebook, which is functioning normally in Pyongyang.

It was still possible to use the app, despite the warnings, on some mobile devices. But attempts on others to post photos or view user galleries through the standard Koryolink connection have been virtually impossible, suggesting that some access was indeed being obstructed.