A number of police forces in England and Wales are reporting the 101 non-emergency phone number is down.
At least 13 forces - including the four Welsh forces and the Metropolitan Police - say there have been technical issues with the line since 09:00 GMT.
The Met Police said calls were not being received via 101 but said the 999 emergency line was unaffected.
There are also reports the 111 NHS non-emergency line has stopped working in Scotland.
Alternative numbers
101 is the contact number for local police in England, Wales, Scotland and Northern Ireland for less urgent matters than a 999 call.
Some forces are asking the public to refer to local police websites or call a landline number.
The following police forces are reporting problems:
- Cheshire Constabulary
- Cleveland Police
- Durham Constabulary
- Dyfed-Powys Police
- Gwent Police
- Hertfordshire Constabulary
- Hampshire Constabulary
- Metropolitan Police
- North Wales Police
- Northumbria Police
- South Wales Police
- Sussex Police
- West Mercia Police
A list of alternative non-emergency numbers is available on the 101 website.
A Met Police spokesman said they were experiencing "technical issues" with 101 and advised people to report non-urgent crime via their website.
"We are working with our service provider to rectify this issue as soon as possible," a spokesman said.
The Home Office, which oversees the 101 line, has yet to issue a comment.
NHS Scotland tweeted: "111 phone service having technical problems across UK this morning. In Scotland NHS 24 available via 08454 242424 for those needing help."