"The government considers it unacceptable and rejects in the strongest terms Ryanair's passing of the special tax on extra profit levied on airlines to passengers," Nagy said in a statement sent to MTI.

"It is especially adverse that Ryanair has started this practice with regard to tickets sold earlier," he added.

Authorities will undertake a thorough investigation with a view to consumer rights and prevent the airline's unfair business practices where possible, the statement said. 

Hungary's government has levied windfall taxes for a period of two years on the banking, insurance, energy, retail, telecommunications, and pharmaceutical sectors, in addition to airlines, to ensure resources to protect the regulated utilities price scheme for households and upgrade the country's military defense.

The statement said the government is "following market trends closely" and will do "everything in its power" to prevent the cost of windfall taxes from being passed on to consumers.

"Investigations will be conducted in each and every case, and firm steps will be taken against harmful practices," it added.

Nagy said he has also initiated a probe to determine if Ryanair's ticket pricing practices comply with all European norms and requirements.

The Budapest Metropolitan Government Office said later on Friday it ordered an immediate consumer protection probe of Ryanair. 

A government decree requires airlines to pay a HUF 3,900-per-passenger contribution for travelers on flights bound for countries in the European Union as well as destinations in Albania, Andorra, Bosnia and Herzegovina, North Macedonia, Iceland, Kosovo, Liechtenstein, Moldova, Monaco, Montenegro, the United Kingdom, Norway, San Marino, Switzerland, Serbia, and Ukraine. The contribution for other destinations is HUF 9,750 per passenger.