WASHINGTON, Nov. 1 - Stepped-up flights by Russian fighters, long-range bombers and tanker aircraft are aggravating security concerns in Europe and the United States is watching them very closely, the Pentagon said on Friday, Reuters reported.

Rear Admiral John Kirby, the Pentagon press secretary, said Russian military planes carried out more flights on Friday over the Baltics, North Sea and Atlantic Ocean, part of what NATO has said is an unusual burst of air activity by Moscow.