In a statement, the Channel tunnel rail operator said it was running a restricted service until Sunday night and recommended that passengers whose trips were not essential should not travel at all.

Eurostar cancelled nine trains on Thursday.

A signal failure was blamed for the two-hour undersea breakdown of a Brussels to London train, as northern Europe shivered in bitterly cold temperatures and snow that has caused transport chaos.

"When the Eurostar was in the tunnel, Belgian signals rather than British signals came into operation for an unknown reason," said a spokesman for SNCF, France's state railway, and the biggest shareholder in Eurostar.

This triggered an automatic emergency stop and caused the delay, he said.

"At first they told us that it was an engine problem," Jonattan Lurasin (26) from Liege in Belgium, told AFP at London's Saint Pancras International station, where passengers from Brussels arrived after their ordeal.

"They tried to restart two or three times, but it didn't work," he added after the stricken train was towed out of the tunnel to Ashford, southeast of London, and passengers transferred to another train to complete their journey.

An announcement at the station, where hundreds of people were left queuing, said there would be an "extremely limited" service during the afternoon and advised people who did not need to travel to change their plans.

On its website, Eurostar said: "Because of the current severe weather conditions Eurostar will continue to run a restricted service up to and including Sunday 10th. If you do not need to travel we recommend you cancel or postpone your trip."

It said it had decided not to run its very early morning services or its late services between London and Paris and Brussels.

Travellers with tickets for late evening trains were advised to come to the station as early as possible and they will be allocated a space on an earlier departure. All other travellers were asked to check in as normal.

In Paris, some 500 to 600 people faced lengthy delays in the cold at Gare du Nord. Loudspeakers regularly announced bad weather was delaying trains, and asked passengers to postpone their travel, with a full ticket refund promised.

Several Eurostar trains broke down in the tunnel on December 19, the Saturday before Christmas, sparking a three-day suspension of service that left tens of thousands of passengers stranded.

Around 2000 passengers in five trains were trapped for up to 17 hours.

The trains' operators blamed that breakdown on snow they said was more powdery than usual, which had filtered into engine compartments and melted once the trains entered the tunnel.

At St Pancras, Nicole Aerts, from Aalter in Belgium, said her journey had been "terrible," although she and her friends ? who had only come to London for the day ? had been well-informed and given water and sandwiches.

The pre-Christmas breakdown was a publicity nightmare for Eurostar, with passengers complaining of being left stranded for hours without information, sustenance or light.

Passengers on the train stuck in the tunnel Thursday seemed relatively happy with how the situation was managed.

Eurostar "made us a good offer... they reimbursed our tickets and gave us new tickets to come back," said Lurasin. "So it's OK."