Russian military jets have violated Estonia's airspace, according to officials.
The Estonian Government said the incident involved three MiG-31 fighter jets which entered the country's airspace without permission and stayed there for 12 minutes.
Foreign Minister Margus Tsahkna said Russia had already violated the Nato ally's airspace four times this year, "which is unacceptable in itself, but today's violation, during which three fighter jets entered our airspace, is unprecedentedly brazen".
He added: "Russia's ever-increasing testing of borders and aggressiveness must be responded to by rapidly strengthening political and economic pressure."
The Estonian Government said the incident involved three MiG-31 fighter jets (file photo)
|GETTY
Estonia said it had made a protest to the top Russian diplomat in the country.
A Nato spokesman said the Russian jets had "violated Estonian airspace", adding "Nato responded immediately and intercepted the Russian aircraft".
"This is yet another example of reckless Russian behaviour and Nato's ability to respond," the spokesman said.
President of the European Commission, Ursula von der Leyen, said: "Europe stands with Estonia in the face of Russia’s latest violation of our airspace.
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"We will respond to every provocation with determination while investing in a stronger Eastern flank.
"As threats escalate, so too will our pressure. I call on EU leaders to swiftly approve our 19th sanctions package."
The incident comes just over a week after Russian drones entered Polish airspace, some of which were downed by Nato jets.
It is the first time a member of the Western military alliance is known to have fired shots during Russia's war in Ukraine.
The incursion by Russia prompted Latvia to temporarily close its airspace near its Eastern border with Belarus and Russia.
Just days later, Russia then entered into Romania's territory.
Romania scrambled fighter jets on Saturday, September 13, when a drone breached the country's airspace during a Russian attack on Ukrainian infrastructure near the border, the defence ministry said.
Defence Minister Ionut Mosteanu said the F-16 pilots came close to taking down the drone as it was flying very low before it left national airspace toward Ukraine.
Some drones which entered Polish airspace were shot down by Nato jets
|DARIUSZ STEFANIUK/REUTERS
Romania, a European Union and Nato state which shares a border with Ukraine, has had Russian drone fragments fall onto its territory repeatedly since the start of the conflict.
Britain's Ministry of Defence (MoD) this week said the UK will deploy RAF fighter jets to Poland as part of a Nato operation to counter aerial threats from Russia.
The RAF Typhoons will join allied forces - including from Denmark, France and Germany - to reinforce Nato's defence along its eastern flank, which stretches from the Baltic states in the north to Romania and Bulgaria in the south.
Sir Keir Starmer has said Britain will continue to "ramp up the pressure on Putin".
Britain will deploy RAF jets to Poland as part of a Nato operation to counter aerial threats from Russia
| MINISTRY OF DEFENCE
"Russia’s reckless behaviour is a direct threat to European security and a violation of international law, which is why the UK will support Nato's efforts to bolster its eastern flank through Eastern Sentry, the Prime Minister said.
"These aircraft are not just a show of strength, they are vital in deterring aggression, securing Nato airspace, and protecting our national security and that of our allies.
"We will continue to stand firm in our support for Ukraine and ramp up the pressure on Putin until there is a just and lasting peace."