Tourists are urged to be careful when visiting popular parts of Greece.
A safety and security warning has come as Britons flock to the country for a football match today.
A fresh update has been given by the UK Government ahead of the UEFA Europa League game that takes place today.
Britons may have travelled to Athens to watch the AEK and Brighton match.
Demonstrations are likely in Athens, particularly on a date next week
PA
The FCO warns: "If you are travelling to Athens for the match, you should plan your movement around the city to arrive at the stadium well in advance of the match kick-off.
"Follow the instructions of the local authorities and take care of your personal possessions including passports, especially in crowds and on public transport."
This comes as holidaymakers visiting lots of popular parts of the country are urged to be vigilant.
Advice explained demonstrations are likely and could have dangerous effects.
"Avoid demonstrations wherever possible and follow the advice of the local authorities," the FCO continued.
"Some demonstrations in the past have turned violent. If you do find yourself unexpectedly near a demonstration, move away to the last known safe place.
"Security forces often use tear gas to break up demonstrations, which can harm your breathing and vision."
They added demonstrations are particularly likely on certain dates, including next week on December 6.
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Britons should be cautious in Greece
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Such protests and demonstrations can happen across the country but they are particularly likely in tourist areas, such as central Athens.
Britons planning a holiday have recently been warned when travelling to a number of destinations.
In other news, cruisegoers have been stranded as a £90,000 luxury three-year cruise is cancelled days before departure.