Hoax bomb threats have hit at least 27 affected flights across Europe from Ireland to Bulgaria, the second wave this week, forcing some ‌to make unplanned landings and prompting fighter jets to escort or intercept others.

While no country has attributed blame for the threats, they come as many European officials accuse Russian authorities of masterminding sabotage and “hybrid attacks” – often cheap, easily deniable and ‌not expected to trigger an armed response.

Denmark, Poland and Romania, all affected by Thursday’s disruptions, have previously accused Russia directly while Germany blamed Russia for an attack on Leipzig airport in August.

Britain has blamed Russia in the past but linked Iran to a suspected plot to attack a US air base.

Russian and Iranian authorities deny any involvement.

French Prime Minister Sebastien ​Lecornu’s office said he had sent fighter jets to intercept an Aer Lingus flight from Dublin to Rome and escort it to an air force base at Evreux after the pilot did not co-operate with authorities as expected. No reason was given for the pilot’s behaviour.

Bulgaria’s air force said its fighter jets had escorted three planes to the ground.

Ryanair planes from Copenhagen and Madrid to Sofia landed as planned, while a flight from London to Sofia was diverted to Plovdiv, Bulgaria’s second city.

Spanish authorities received three emailed bomb threats within 20 minutes involving two Air Europa departures from Madrid to Paris and four inbound Iberia flights from Rome and Milan, Spain’s Guardia Civil said.

Several aircraft in ⁠Madrid were halted or returned to their stands and passengers disembarked while planes were inspected.

In Warsaw, a LOT flight to ‌Paris was stopped as ​it taxied towards take-off and passengers were transferred to another aircraft.

A flight from Cork in Ireland was delayed 90 minutes after the airport received a threat, the airport operator said.

At Copenhagen airport in Denmark, two planes were ​searched, police said.

Italian media ‌reported that a Wizz Air flight from Milan to Warsaw had been diverted to Vienna.

Two Easyjet flights from the UK, one flight from Ireland and one from Greece landed as scheduled in Prague after receiving bomb ​threats, as did a Finnair flight from Helsinki to Vienna, a Polish LOT flight from Warsaw to Brussels, a Hungarian Wizz Air flight from Milan to Bucharest and an Air Serbia flight from Belgrade, also to Bucharest.

The Italian news agency ANSA said two planes had landed as planned in Milan while a person familiar with the matter said Italy’s air force escorted a Finnair plane coming from Helsinki to its ​scheduled ​landing in Rome.

The operator of Rome’s Fiumicino Airport said there had been no disruption to ​services, and that departing passengers were philosophical.

“It’s more complicated with everything that’s going on but what else are we ‌going to do?” said Spaniard Lucia Parga.

“We still have to get around. So, well, we just have to deal with it as best we can.”

Another traveller, Gabriele Franzese, added: “You can’t worry too much about every piece of news. If the plane crashes, so be it. If it’s meant to happen, it’ll happen anyway.”

Joji Waites, director of flight safety for the British Airline Pilots’ Association, said it was industry practice that airlines did not act on threats unless they had been rated credible by assessors.

Eliran Almog, CEO of aviation cybersecurity firm Cyviation, said the hoaxes could serve both to disrupt operations and to observe how airlines, airports and authorities respond.