The Foreign and Commonwealth Office (FCO) has updated its travel advice to Greece, warning of a general threat of terrorism.
Its advice, which was reviewed and reissued on December 4, said there could be disturbances in major urban centres throughout December, the first anniversary of serious riots that followed the shooting of a Greek teenager in 2008.
Brits travelling to Greece should exercise caution and avoid demonstrations, said the FCO. Attacks could be indiscriminate, including in places frequented by expatriates and foreign travellers.
Yesterday, according to the BBC, Greek police fired teargas at demonstrators in Athens who had assembled for a memorial for the teenager. A second memorial and rally is due to take place today. There were also outbreaks of violence in Thessaloniki.
UK nationals who encounter trouble while in Greece will be transferred to the Greek emergency services if they call 999 from a UK mobile.