Passengers queue at the entrance to Eurostar in St Pancras International station in central London, on Sunday. AP

Eurostar trains will run as normal Sunday, the company said, hours after an entire day's services had to be cancelled, causing misery for tens of thousands of New Year travellers.

Saturday's massive disruption left some travellers in tears as they arrived at London's St Pancras Station to discover that two flooded tunnels in southern England had blocked the high-speed rail line to the continent.

Other travellers were left stranded in mainland Europe.

Earlier, High Speed 1 (HS1), which runs the railway line, had warned the volume of water in the tunnels was "unprecedented" and would take time to clear.

But later Saturday Eurostar announced that services would run as scheduled on Sunday as "at least one tunnel can now be used".

A service update is displayed as passengers stand at St Pancras International Station in London. Reuters

"We're able to confirm that we'll be running our planned timetable tomorrow," the company posted on X, formerly Twitter. "Our stations will be extremely busy due to today's disruption."

Holiday plans 'ruined'

Dismayed Eurostar passengers earlier described their disappointment as their New Year plans were left in tatters by the cancellations, which affected an estimated over 30,000 people.

Newly-weds Nicole Carrera, 29, and her husband Christopher, 31, visiting from New York, said their plans to spend New Year's Eve at Disneyland Paris had been "ruined".

After earlier cancelling all trains up to 4:00 pm UK time (1600 GMT), Eurostar said flooding in the two tunnels had "not improved".

That had forced it to "take the unfortunate decision to cancel all services for the rest of the day".

Australians Christina David, 25, and Georgina Benyamin, 26, from Sydney, had planned to make Paris their final stop in Europe before flying home.

David said she felt "frustrated, angry, sad", adding that "there were lots of people crying" and that they now had nowhere to stay.

People walk outside the St. Pancras International Station in London. Reuters

Eurostar runs services from London to Paris, Brussels and Amsterdam.

The services were cancelled after the flooding occurred near Ebbsfleet International station in Kent.

Year of travel chaos

Simon Shaw, 36, and his wife Heather, 37, from central England, had been due to travel to the French Alps for a skiing holiday with friends and family.

"We just arrived and saw everything was cancelled this morning... it was chaos," Simon Shaw said.

The Eurostar chaos topped off a year of travel disruption for UK travellers due to strikes, storms and other problems.

Travellers to France in April endured waiting times of up to 16 hours at Dover due to larger than expected numbers and weather conditions.

In August, flights to and from the UK were hit by a technical fault affecting air traffic control systems, while in November Storm Ciaran saw ferry crossings and flights cancelled.

More than a year of walk-outs by rail workers over pay and conditions amid a cost-of-living crisis has also hit travellers.

Although the RMT rail union last month said its members had voted in favour of a pay deal, the Aslef union, which represents drivers, has yet to come to an agreement.

Eurostar is owned 55.75 percent by French state-owned SNCF Voyageurs.

It almost went bankrupt during the Covid-19 pandemic but was saved with a 290-million-euro bailout from shareholders including the French government.

Agence France-Presse