Extra police patrols have been put in place after 999 services went down across “significant” parts of Dundee, Fife and Tayside.
People living in the affected areas have been urged to use a mobile phone or visit an emergency service station, when possible.
Police Scotland issued a statement saying that BT engineers were working to fix the issue.
More officers have been placed on patrol in the meantime, with the loss of service being described as “significant”.
The statement read: “Police Scotland have been advised by British Telecom that there is a significant loss of the 999 service in the wider Tayside and Fife areas at present.
“Scottish Fire and Rescue and the Scottish Ambulance Service have been advised.
“If you need to ring 999 you are advised where possible to use a mobile phone, or attend at your nearest Police Office, Fire Station, or Ambulance Station. Extra Police patrols are out in the affected areas.
“BT engineers are currently dealing with the issue, and hope to have service resumed at the earliest opportunity.”
BT have been approached for comment.