The websites of several high-profile companies including HSBC, Airbnb and British Airways appear to have been hit by outages.
A message on the BA website read: “Service Unavailable – DNS failure. The server is temporarily unable to service your request. Please try again later.”
And a message on Airbnb’s site said: “This site can’t be reached.”
HSBC’s website had a similar message.
It is not known what has caused the issues.
And there are reports other airlines and major companies are also affected, as well as the 911 service on the east coast of the US.