Eurostar passengers face further disruption after one of its high-speed trains got stuck in the Channel Tunnel again Thursday, the operator said, weeks after a major breakdown due to the cold.

The cause of the latest two-hour blockage in the tunnel between Britain and France was not immediately clear, but it came as northern Europe shivered in bitterly cold temperatures and snow that has caused transport chaos.

"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 there would also be a "restricted service over the next few days" and the last trains Thursday would run earlier than usual, adding that passengers could get a refund or change their tickets for free.

The train operator is still unclear on what caused the breakdown.

"We have fixed the original problem (in December). We don't know what the cause is today. We will do everything we can to get to the bottom of this as soon as possible, of course," spokesman Bram Smets told AFP in Brussels.

Speaking shortly after the breakdown, he said: "We are not allowing any train to enter the tunnel at present, they are waiting. We don't want any (more) trains to be blocked in the tunnel if we don't know what happened."

An official at St Pancras said two trains had left London since then but had to turn back, although this was not immediately confirmed by head office. A spokesman insisted: "No suspension is expected. The trains continue to run."

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

Around 2,000 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 Saint 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."