The first missiles are being thrown at police guarding the Greek Parliament. So far the police are refusing to be provoked.
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The move comes amid a motion of no confidence that was tabled against Labour leader Jeremy Corbyn.
The first anniversary of the Sousse terrorist attack - which left 30 Britons dead - will be marked by families of the victims on Sunday.
Since Friday's EU result, the Liberal Democrats have recorded thousands of voters signing up to become members.