The alleged incursion comes at a moment of increased tension on NATO's eastern border, after Poland last week complained that around 20 Russian drones overflew its territory. Moscow denied Poland was targeted.

Russia is fighting a war in Ukraine and often tests Western air defences, but Estonia complained that the sorties have become more provocative in recent months.

"Russia has already violated Estonia's airspace four times this year, which in itself is unacceptable. But today's incursion... is unprecedentedly brazen," Foreign Minister Margus Tsahkna said.

"Russia's increasingly extensive testing of boundaries and growing aggressiveness must be met with a swift increase in political and economic pressure," he said.

Estonia's defence ministry also confirmed the incursion.