Eurostar has urged customers not to travel on Thursday after it was forced to cancel trains when strike action hit the cross-Channel route.
The company said it had to halt services at midday until 15:30 due to a “last-minute strike” at Getlink, the Channel Tunnel operator.
The disruption emerged as many people start travelling for the Christmas holidays over the next few days.
Eurotunnel has also temporarily suspended all LeShuttle services.
The LeShuttle service carries cars through the tunnel on trains.
“We apologise for the delay to your journey.” Eurotunnel said. “Further updates will be provided shortly.”
In a statement, Eurostar said: “Customers affected will receive direct communication about their journey and we recommend that travellers postpone their travel today if possible.
“We are closely monitoring the situation as it evolves, and any further updates will be communicated as soon as possible.”
Getlink, the French company which operates the Channel Tunnel, said: “Today’s call for strike action by representatives of Eurotunnel’s French site staff unions has resulted in the complete interruption of service and the closure of our terminals in France and the UK.”
Chris Tirifahy-McCabe and his wife were planning to travel to Brussels to visit family. He’s currently stuck at St Pancras and is trying to make alternative travel arrangements, along with hundreds of others.
“All Eurostar services have been suspended until further notice”, he told the BBC. “There are around 500 people stuck past security waiting.”
“It’s an unexpected strike and that’s all they’re saying. There’s been no real communications”
“No one knows whether to leave or stay”, he added.
Transport networks are gearing up for one of the busiest periods of the year, with many travelling to visit family and friends.
Travel in some parts of the UK has already been disrupted by strong winds from Storm Pia.
Rail operator TransPennine Express has issued “do not travel” advice to customers for its services to and from Edinburgh before 15:00.
British Airways says it has had to adjust its flight schedule on Thursday as a result of air traffic control restrictions put in place in response to the storm.