At least seven flights and a cruise ship in Europe received bomb threats on Tuesday, CNN reports, citing Reuters. At least two flights to Warsaw, two to Sofia, two to Rome and one to Murcia in Spain were threatened, CNN says. Another flight to Sofia had been threatened a day earlier.

Authorities diverted a LOT flight from London that was meant to land at Warsaw's Chopin Airport to nearby Modlin Airport, NBC News reports. Modlin was briefly closed while the plane was searched, and it reopened after no device was found, NBC says.

In Spain, parts of the airport in Murcia were cordoned off after a threat was reported on a Ryanair flight from Manchester, NBC reports. Officials said the report proved to be a hoax. Italian fighter jets escorted a Ryanair plane into Rome after a warning about a flight from Dublin, The Guardian says.

Downing Street called the threats “malicious hoaxes,” The Guardian reports. A UK Department for Transport source said the low-level threats were “not credible” and that passengers should not be concerned, the paper says.

There was no claim of responsibility and officials did not blame anyone, CNN reports. Investigators said there was no immediate evidence of a hostile state behind the threats, The Guardian says.

Rhys Jones of the aviation risk firm Osprey Flight Solutions said seven confirmed threats against flights in one day was exceptional, CNN reports. He said the lack of a clear target suggests the aim is general disruption to air travel.

Four of the flights were run by Ryanair, and the others by Wizz Air, LOT and SAS, The Guardian reports.

What we know: Flights across Europe were hit by bomb threats, and no devices were found.
What we don't: Who sent the threats and whether they were linked.