The offices of Irish National broadcaster RTE after staff were evacuated from the site following a bomb threat. ( Reuters: Natalia Campos )
Several media outlets in Europe have reported receiving bomb threats.
It follows a spate of threats to passenger flights across the continent forced airlines to ground or escort planes.
The signature attached to the threats matches the name of a far-right movement in Russia, but the link is yet to be confirmed.
Newsrooms in Ireland and Bulgaria have received emailed bomb threats from a purported "Mikhail Andropov", claiming responsibility for a widening wave of hoax threats disrupting passenger flights across Europe.
The messages, sent on Friday, local time, to Bulgaria's Nova TV and the Irish public broadcaster RTE, which evacuated its offices, were headlined "Message to the West" and portrayed the threats as the prelude to a series of attacks on means of transport across Europe.
The British broadcaster Sky also said it had received a security threat.
It comes as Ireland is scheduled to host a high-profile EU meeting on Russia Ukraine relations next week. ( Reuters: Natalia Campos )
Reuters was not able to establish the identity of the sender, the origin of the emails, or whether they had in fact come from the same source as the threats to any or all of the dozens of flights affected since Tuesday.
No explosive devices have been found and all planes have landed safely.
On Thursday, local time, airlines and airports in Italy received threatening emails purporting to be from a banned Russian campaign group, although their origin could not be verified.
Spain's foreign minister said the continent appeared to be facing "hybrid aggression and a form of psychological warfare".
Around half a dozen flights were disrupted in some way on Tuesday and more than two dozen on Thursday, some of them making unplanned landings or being escorted to their destinations by fighter jets.
On Friday, jets escorted airliners flying from Brussels to Sofia and from Prague to Bucharest and Cyprus through Hungarian airspace due to bomb threats, Hungarian Defence Minister Romulusz Ruszin-Szendi said.
He also said NATO had ordered an air patrol near the Hungarian-Romanian border, the first report that the Western defence alliance had become involved.
Danish police said threats had been directed at traffic at Copenhagen airport but that there appeared to be no danger to passengers. The airport said it was "operating normally".
Czech police registered bomb threats to nine flights departing from or arriving in Prague. An airport spokesperson said no flights had been cancelled as a result.
An Aer Lingus Airbus seen at Evreux military air base after a flight from Dublin to Rome was diverted to France. ( AP: Thomas Padilla )
However, an Italian airport authority source said a Wizz Air flight from Prague to Rome had been diverted to Venice.
France said four new bomb threats had been made to aircraft flying over French territory, and that all had landed safely.
A Ryanair flight from Rome landed as scheduled in Lisbon, CNN Portugal reported.
Security experts said on Thursday that the threats had the hallmarks of a coordinated "hybrid attack", although it was always possible that individuals were issuing copycat threats or acting on personal grievances.
While no country has attributed blame for the threats, they come after a wave of sabotage attacks and attempts on targets across Europe ranging from German electricity substations to defence-related facilities in the Baltic region, supermarket refrigerators in France and elsewhere and Leipzig airport in Germany.
Passengers check their flight at Leonardo da Vinci International Airport after a flight from Dublin to Rome was diverted to France amid reports of bomb threats. ( AP: Gregorio Borgia )
Many officials have linked the campaign to Europe's support for Ukraine in its war against invading Russian forces, accusing Moscow of a campaign of "hybrid" disruptions that are essentially cheap to execute, easy to deny and not expected to trigger an armed response. Moscow has strongly denied involvement.
Spanish Foreign Minister José Manuel Albares told the national broadcaster TVE that, while it would take time to determine exactly what happened, "it cannot be mere coincidence that so many incidents with exactly the same modus operandi are happening across Europe".
"The most reasonable assumption is that we are facing an attempt at hybrid aggression and a form of psychological warfare," he said, adding that Europe must be prepared for more such challenges.
On Thursday, an airport source in Italy said bomb threats had been sent to several airlines and airport operators in Rome and Milan claiming to be from "fighters of the Male State", a far-right anti-feminist movement banned in Russia.
Reuters could not confirm who had sent the email. Vladislav Pozdnyakov, a Russian blogger who set up Male State in 2016, said it no longer existed and was not involved in any way.
