Following a report that a drone had entered Lithuania’s territory from Belarus, Vilnius Airport was closed for less than an hour on Saturday, and NATO’s Baltic Air Policing fighter jets took off.

According to Reuters, Lithuania’s National Crisis Management Centre said officials were investigating the cause of the drone alert.

Similar incidents have been repeated in European countries in recent months. Denmark’s intelligence service said last week that Russia is likely to step up its hybrid operations against the West, and on Monday, Kaja Kallas, the EU foreign policy chief, said the information available indicates that Moscow is preparing further sabotage actions in Europe.

On Tuesday, Estonia’s government also announced that with “full confidence” Russian special services had ordered arson deliberately at a defense equipment factory in Tallinn.

Russia denies carrying out hybrid attacks against Western countries.