Trains to and from Paris have been cancelled, an area evacuated and part of the main ring road temporarily closed after an unexploded World War Two bomb was found on tracks leading to Gare du Nord station.

Eurostar services at Gare du Nord were scrapped for the day, after the 500kg bomb was found on tracks in the Paris suburb of Saint-Denis during overnight work.

Homes with windows in a 500m (1,600ft) radius of the bomb were evacuated and part of the Paris circular périphérique was shut as the clearance operation took place.

French Transport Minister Philippe Tabarot said local rail services at Gare du Nord would not resume until late afternoon at the earliest.

Tabarot said on Friday morning that a bomb disposal team was on the scene and there was nothing to worry about. “If we get the green light from the police chief in the coming hours, part of the service could – and I mean could – start up again after 16:00 (15:00G),” he said.

The bomb was discovered 200m away from the busy Paris périphérique, about 2.5km (1.5 miles) north of Gare du Nord, Europe’s busiest train station.

A nearby short northern stretch of the ring road and the A1 motorway were shut around Porte de la Chapelle.

Authorities in Saint-Denis said there were six schools and a care facility for elderly people inside the evacuation zone, but they were not at risk, because they did not have windows overlooking the area.

Eurostar services were running normally between Brussels and Marne-la–Vallée to the east of Paris as well as trains between London and Brussels and London and Amsterdam.

High-speed TGV trains into Gare du Nord were also badly hit, although some services were diverted to Gare de Lyon in Paris.

“Due to the discovery last night of an unexploded World War Two bomb during work carried out on the tracks in St Denis (North of Paris), traffic has been completely halted to and from Gare du Nord,” Eurostar said.

Passengers could exchange their tickets for free to travel at another date or time in the same class, subject to availability, the train company said.

“Eurostar sincerely apologises for the disruption and understands the inconvenience this may cause,” the company added.

Queues were beginning to form by 08:30 GMT at St Pancras train station in London as passengers tried to work out what they could do.

One group was approaching the front of the line after a two-and-a-half hour wait.

Their 07:00 GMT train was cancelled and they planned to travel to Lille and make a three-hour bus journey to Paris.

Jess Sayer from Norwich told the BBC on Friday morning that she was stuck in Paris with her husband and best friend after celebrating her 40th birthday on Thursday.

“We’re frantically on our phones trying to find out what to do,” she said, explaining they had not been able book a train for Saturday via the website.

“We just tried to get a flight. All the flights are booked up so at the moment we are completely stuck in Paris with no way of getting home,” she said. “Do we get a hotel and risk trying to get the Eurostar home tomorrow? Or look into ferries?”

Her friend, Sarah Fitzgerald, said she was trying to get back to London to help her family prepare for a funeral on Monday.

Ivana Koralek told the BBC she had decided to cancel a trip to see her elderly mother and nephew in France.

She said she had been unable to rebook for three weeks’ time because ticket machines in the station did not offer the discount she had originally received.

Karen Hamblin, from Chester, had travelled to London on Thursday evening to catch a Friday train to Paris for a three-day getaway to celebrate her husband’s birthday.

She said she was told at about 07:00 that their train was cancelled.

“As we were effectively stranded, we have decided to transfer our ticket and travel to Lille,” she said. “Lunch in Lille and [we’ll] then work out how to get to Paris from there!”

Additional reporting by Tom Symonds