New Delhi, Nov. 4 -- He gave few details but said that "individuals with flashlights" had been observed in the border area. The Polish guards prevented any incident from happening.

Poland, NATO's largest member on the alliance's eastern flank, borders Russia's Kaliningrad exclave to the north and Belarus, Moscow's close ally, to the east.

"Just after midnight, I received information from the border guards that disturbing movement had been observed on the Polish-Russian border," Tusk said.

The Polish police, working with the military, border guards and intelligence services, have been carrying out additional activities recently to strengthen security along Poland's borders with Russia and Belarus, including near the Russian exclave of K...