On Friday morning, less than 48 hours after President Obama delivered a speech in Estonia warning that Russian aggression against Estonia could trigger war with the US and NATO, Russian security forces have seized an officer with Estonia's state security bureau at gunpoint and taken him into Russia.

Estonia says the officer was kidnapped (or "abducted") on Estonian soil and taken across by force. Moscow says the Estonian officer was on Russian soil and detained with a gun, 5,000 euros and "materials that have the character of an intelligence mission." Nearby Estonian police radios were reportedly jammed during the incident.

The incident comes at a moment when Europe and the US are extremely concerned that Russia might attempt military action against Estonia as it has against Ukraine. Just on Wednesday, the United States publicly committed to Estonia's military defense, meaning that a Russian invasion of Estonia would trigger war between Russia and the US, a prospect so dangerous that the world managed to avoid it throughout even the Cold War.

"Unidentified persons coming from Russia took the freedom of an officer of Estonian Security police officer on the territory of Estonia," Estonia's state prosecutor's office announced, shortly before Russia claimed responsibility. "The officer was taken to Russia using physical force and at gunpoint."

The statement continues: "The officer was fulfilling his duties in connection to preventing a cross-border crime in taking place. The use of smoke grenades and intense interference with operative radio connections preceded the incident."

Estonian President Toomas Hendrik Ilves tweeted almost immediately about the kidnapping, indicating that the government considers it a major incident. His government quickly summoned the Russian ambassador, and Estonia's interior minister said of the attack, "This kind of behavior is unacceptable."

The Estonian state security officer is identified as working on counterintelligence and organized crime — a confusing combination, and one that does not shed much light on whether he was working, at the time, in his capacity against organized crime or against foreign intelligence agencies.

Fears are extremely high across Europe that Russian President Vladimir Putin might attempt some sort of aggression against Estonia or Latvia, two Baltic states on the Russia border that are formerly part of the Soviet Union. Putin invaded Crimea in March and eastern Ukraine in August, both times ostensibly to "protect" the large populations of ethnic Russians and native Russian-speakers in those regions. Also both times, he started by using unmarked Russian soldiers to stir up isolated violent incidents.

One quarter of Estonia's population is ethnic Russian — even larger than in Ukraine — and much of it concentrated on the border with Russia. Estonia's third-largest city, Narva, is about 90 percent Russian; just the sort of majority Russian enclave the Putin has asserted control over in Ukraine, and to a lesser degree in Georgia and Moldova. And Estonia, even more so than Ukraine, since breaking away from the Soviet Union has aligned itself with the West against Russia.

This fear of Russian aggression in Estonia and neighboring Latvia is a primary reason why President Obama traveled to Estonia's capital this week. In his speech, Obama explicitly warned Russia that the United States and the other members of NATO (including the UK, France, and Germany) would defend Estonia and Latvia, also NATO members, just as they would defend "Berlin and Paris and London." It was a clear warning to Russia not to do in Estonia what it had done in Ukraine — thus showing how concerned the world is about exactly that happening.

This incident, happening when it has, at the very least highlights the extreme level of concern in eastern Europe that Russia (which is also sending military planes into Finland's airspace) will target Estonia next. Hopefully, though, the incident will come to nothing.

To learn more about the conflict between Russia and Ukraine, read the full explainer, and watch the two-minute video below: