A series of fires has hit French high-speed rail lines, hours before the Paris Olympics opening ceremony.
Rail company SNCF says it's a "massive attack aimed at paralysing the network"; France's transport minister condemns the "co-ordinated malicious acts".
Some 800,000 customers will be affected with disruption expected all weekend, the rail firm says.
One in four Eurostar services between London and Paris will be cancelled until Monday.
Majority of Eurostar passengers will be able to travel today
Eurostar’s Chief Commercial Officer says he’s confident most people in the UK will still be able to get to Paris for the Olympic Games despite widespread rail disruption in France.
François Le Doze says the majority of passengers hoping to leave today will still be able to do so.
Trains will have to run slower along certain sections in France after the network was attacked and damaged.
Le Doze says extra staff at St Pancras International have helped keep things calm in London and that overall there is still a general mood of excitement.
Security presence at Gare du Nord station in Paris
French military personnel and police officers have been seen at the Gare du Nord station in Paris.
Passenger Sarah Moseley says the disruption was "a hell of a way to start the Olympics" as she tried to travel to London.
Corey Grainger, also trying to head to London, says "they should have more information for tourists".
SNCF says the situation should last "at least all weekend" but that teams are already on site carrying out checks and beginning repairs.
The operator has advised all its passengers to postpone their journeys and "not to go to the station".
