Russian military’s Sukhoi Su-27 violated Estonia’s airspace, the Estonian ambassador to NATO said Friday on Twitter. This comes a day after Finland accused Russia of breaching its airspace.

It was not immediately clear when the latest violation happened, however, according to Ambassador Lauri Lepik’s Twitter feed, Russia’s activity in the Baltic region increased over the past 48 hours. Following this, Estonia’s foreign affairs ministry summoned the Russian envoy.

The Finnish Defense Ministry said that a Russian Su-27 aircraft was involved in “suspected violation” of Finland’s airspace on Thursday. The breach allegedly lasted about a minute as the jet entered just over half a mile into the Finnish airspace.

“Later in the evening there was another suspected violation of airspace by the same aircraft type. The Air Force identified and described both machines,” the Finnish Air Force said in a statement Friday.

However, the Russian defense ministry denied any airspace violations and said that a Su-27 jet was on a training mission over the neutral waters of the Gulf of Finland on Thursday.

“A Russian Su-27 combat plane on October 6, 2016, carried out a training flight over neutral waters of the Bay of Finland,” the Russian ministry said in a statement. “The plane did not deviate from the established route, which is confirmed by means of objective monitoring.”