At least 21 aircraft and several airports across Europe have been targeted by bomb threats in the second such incident this week, with the UK calling it a "malicious hoax".

Flights to Austria, Belgium, Bulgaria, the Czech Republic, France, Italy, Poland and Romania were affected. An Aer Lingus plane from Dublin to Rome was diverted to an air base in France and Italian fighter jets escorted Finnair's Helsinki-Rome flight.

EasyJet said its flights from Newcastle and Glasgow were met by police in Prague as a precaution. London Heathrow and Birmingham airports received threats that were assessed as not credible.

No explosives have been found during searches, and it is not clear if the incidents, some claimed by a little known group, are related.

The airport authorities in Italy's capital Rome said the hoax threat against two inbound flights received on Thursday had come by The warnings were signed on behalf of a group or individual calling themselves "Fighters of the Male State", claiming to be targeting a "feminist regime" and wanting to "make our mark on history". They threatened to "turn the skies red" with explosions.

These details were first reported by Italian media and then confirmed to the BBC by Aeroporti di Roma, which manages both of the city airports.

"Fighters of the Male State" likely refers to the Russian group "Muzhskoi Legion" ( "Male Legion") - an ultra-right group with such extreme views it was banned by a Moscow court in 2021. Yet it retained tens of thousands of online followers as it cheered on the full-scale Russian invasion of Ukraine in the following year.

But that email, even if genuine, is unlikely to provide the leads that police and airport authorities need to pin down who is generating these hoaxes and why.

UK Transport Secretary Heidi Alexander described Thursday's incidents as "malicious hoax threats." She said the government was taking "these threats seriously", stressing that there were "established processes for dealing with hoax and malicious threats".

A UK government spokesperson later said the threats reported "in the early hours" of the day had been "resolved", without giving any further details.

Heathrow later said in a statement it had received a threat earlier in the day which was "deemed not credible", adding there was "no risk to passengers, colleagues or the aircraft".

"There are robust UK aviation security standards in place to assess and safely manage these types of situations," the statement said.

Meanwhile, a Birmingham Airport spokesperson told the BBC it had received a threat, after which "processes were immediately initiated in conjunction with emergency services and partners". The following flights were targeted by threats on Thursday: Aer Lingus said its flight from Dublin to Rome diverted to Normandy, landing safely. The company added that it was working to "re-accommodate customers to their final destination as soon as possible".

Two Finnair flights from Helsinki landed at their destinations as normal, the airline said. One was escorted into Rome's Fiumicino airport by Italian Air Force fighter jets, Aeroporti di Roma told the BBC, while the other landed in Vienna, Austria Wizz Air said two flights which departed Milan were affected - one was heading to Warsaw, before being diverting to Vienna; the other landed safely in Bucharest, with teams inspecting the aircraft Polish airline LOT said its flight from Warsaw to Brussels landed as planned, and "no suspicious items were found".

Another LOT flight from Warsaw to Paris was stopped before take-off and the plane and baggage underwent a security screening, with no hazardous items found Three Ryanair flights landed in Bulgaria, according to Bulgarian media - one from Copenhagen and another from Madrid landed in the capital Sofia, while a third coming from London bound for Sofia landed in Plovdiv.

The flights were escorted by Bulgarian air force fighter jets No explosives were found on four flights which landed in Prague, Czech police said.

EasyJet later said its flights from Newcastle and Glasgow were among those affected. "Passengers on both flights disembarked normally," the company said Aegean Airlines said it "was informed of a bomb threat" concerning two of its flights from Thessaloniki in Greece to Milan, and also from Athens to Vienna.

It said threat was "unfounded", and both flights departed from the respective airports"

A Ryanair flight from Porto in Portugal landed safely in Milan as planned, with bomb disposal experts checking them on arrival, Italy's Ansa news agency reported Spain's airport authority said it had received bomb threats affecting three flights at Madrid airport, but any threat was ruled out following inspections.

Iberia later said two of its flights - Milan-Madrid and Rome-Madrid - were affected.

It was not clear whether the third plane was the above reported Ryanair Madrid to Sofia flight Air Serbia said its flight from Belgrade to Bucharest "landed safely at its destination airport", and after checks, a reported bomb threat was "assessed as unfounded" Emily Noble, who was aboard the diverted Aer Lingus plane from Dublin to Rome, said she was about an hour into her flight to attend a friend's wedding in the Italian capital when passengers were told about a "technical" problem.

Later, as the Aer Lingus plane began circling for an unplanned landing in France, the pilot said there was a "security" issue, the 26-year-old from Dublin told BBC Verify.

On board it was "an odd experience," Noble said. "It was worrying because we didn't know what was going on, but we were all trying to be as calm as we could." Noble says she could hear fighter jets during the landing and saw one touch down behind the aircraft.

After landing at the Évreux-Fauville air base in Normandy, passengers learned the flight had been the subject of a bomb threat.

Noble said they remained on board for two-and-a-half hours while police and military personnel carried out checks, including searches with sniffer dogs.

The passengers were later told they would be taken to an airport in Paris and another plane would fly them on to Rome.

Philip Baum, professor of aviation security at the University of Coventry, said the industry "faces multiple bomb threats every single day" but he had been "surprised" by this week's incidents.

A flight is diverted "only when the threat is credible and the authorities believe there is a potential of explosive device on board", he said.

He said the concern was that "if you issue enough hoax threats, then complacency could set in and a real threat could be ignored - or they could be a diversion".

Marco Chan, an aviation expert at Kingston University, told the BBC the threats were "most likely a hoax, but the system is right to treat it as real".

He said they were being viewed by some experts as "possibly part of a pattern of cheap, deniable disruption" to air travel.

Hoaxes can also come from copycats, he said, but "three days of incidents is too small a sample to separate coordination from contagion".

Two days ago, seven European flights, including two from the UK, were searched after bomb threats were made. No explosives were found on any of the planes after searches.

On Monday, a Wizz Air flight travelling from London Luton Airport to Sofia was escorted by a Hungarian fighter jet to Budapest after a mid-air bomb threat.