A NATO military plane on Wednesday approached the plane of Russian Defense Minister Sergei Shoigu above the Baltic Sea, Russian news agencies reported, the third such encounter in three days.
A NATO fighter jet tried to approach Shoigu's plane but a Russian escort plane intervened to defend it, Interfax news agency reported, citing journalists accompanying the minister.
The escort plane, a Sukhoi SU-27, demonstrated it was armed by rocking its wings, after which the NATO plane flew off, Interfax reported.
Russian state television aired defense ministry footage of the incident, reporting that it took place over neutral waters.
NATO and national air forces decided to monitor flights after last week tracking "an unusually large number of Russian military aircraft flying over the Baltic Sea," a NATO spokesman said in a statement sent to AFP.
NATO insisted the crew's actions were "routine" to identify the plane while "maintaining a safe distance at all times" and then break away.
Shoigu on Wednesday was flying to Kaliningrad, a highly militarized Russian exclave on the Baltic Sea, to take part in a meeting with defense officials there.
At the meeting, he warned that "the situation near Russia's western borders is tending to get worse," the ministry said on its website.
"This is tied with the upsurge of military activity of NATO countries in Eastern Europe," Shoigu added.
The meeting came after NATO held military exercises over the weekend in Poland on the Lithuanian border close to Kaliningrad.
NATO is deploying four international battalions in Poland and each of the former Soviet Baltic states -- Estonia, Latvia and Lithuania.
Moscow sees the NATO build-up in the region as demonstrating a desire to contain Russia.
On Wednesday, Sweden summoned Russia's ambassador after a Russian Sukhoi fighter jet flew unusually close to a Swedish reconnaissance plane above the Baltic Sea.
"The Russian behavior is unacceptable" and had increased the risk of a serious incident, Swedish Defense Minister Peter Hultqvist told the TT news agency.
That incident, in international airspace, happened on Monday, a Swedish army statement said.
Also on Monday, a Russian fighter conducted an "unsafe" intercept of a US reconnaissance plane over the Baltic Sea, the US military said Tuesday.
Russia's defense ministry said, however, that its fighter plane reacted after the American reconnaissance plane made a "provocative turn" towards it, while another US reconnaissance plane entered the same area 10 minutes later.
Russian fighter jets routinely approach and identify aircraft in the skies over the Baltic and Kaliningrad, but most of these actions stay within safe limits.
Both Washington and Stockholm said the latest incidents went beyond those limits.
The protests come at a time of heightened tensions between Russia and the United States over Syria, where they are backing different sides in the conflict.