HELSINKI — NATO member Estonia said Wednesday that two Russian fighter jets violated its airspace, in what it claimed was the fourth such incident this year.

Two Russian Sukhoi Su-35 fighters entered the Baltic country’s airspace in the vicinity of Hiiumaa, a Baltic Sea island belonging to Estonia, without permission and spent less than one minute there Tuesday morning, Estonia’s military said in a statement.

It added that the transponders on the Russian planes weren’t switched on, they hadn’t filed a flight plan and there was no two-way radio communication with the Estonian air traffic service.

The Russian Embassy’s charge d’affaires was summoned to the Estonian Foreign Ministry and handed a note on the incident.

In a quick response, Moscow denied the air intrusion and said the planes had performed a routine flight over the international waters of the Baltic Sea on Tuesday.

“The flight took place strictly in accordance with the set route. During the flight, the planes did not deviate from their route, which is confirmed by air situation data,” the Russian Defense Ministry said, as quoted by the news agency Interfax.

European Union member Estonia has recorded numerous air violations by Russian aircraft — civilian and military — in past years and made repeated protests to Moscow.

Relations between Estonia and Russia have remained icy since the collapse of the Soviet Union. The two countries have yet to ratify a border treaty nearly 30 years after Estonia, a former Soviet republic, regained its independence.