DOD tracking 'unusual' military activity by Russia

The Pentagon says it is closely watching "unusual military activity," including a buildup of troops, inside Russia, near Ukraine's borders.

"It's unusual in its size and scope," said spokesman John Kirby in a briefing Wednesday with reporters, adding, "We remain concerned about that."

Ukraine's Defense Ministry said last Wednesday that about 90,000 Russian troops are stationed not far from the border and in rebel-controlled areas in Ukraine's east.

Russia has cast its weight behind a separatist insurgency in Ukraine's east that erupted shortly after Moscow's 2014 annexation of Ukraine's Crimean Peninsula and has left more than 14,000 people dead. Russia has repeatedly denied any presence of its troops in eastern Ukraine.

Earlier this year, a massive buildup of Russian troops in the Russia's west raised concern in Ukraine and in the West, fueling fears of an escalation of large-scale hostilities.

Russian officials said the troops were deployed for maneuvers, casting them as part of measures to counter security threats posed by the deployment of NATO forces near Russian borders. Russia and the alliance also have blamed each other for conducting destabilizing military exercises near the borders.

Kirby said the U.S. urges Russia "to be transparent with the international community about what this means, what they're doing and to respect the international community's will about Ukrainian sovereignty and territorial integrity."