Story highlights Russian bombers fly off Guam, California, general says

Increases related to tensions in Ukraine, Air Force commander says

Russians gathering intelligence, showing capabilities, general says

Russia has stepped up military activity in the Pacific, including sending long-range bombers on flights off the coast of California and around the island of Guam, as tensions have risen in Ukraine, a top U.S. Air Force general said Monday.

What Russia is doing in Ukraine and Crimea has a direct effect on what's happening in the Asia Pacific," Gen. Herbert "Hawk" Carlisle said in a presentation to the Center for Strategic and International Studies in Washington.

"They've come with their long-range aviation off the coast of California; they circumnavigated Guam," Carlisle said, showing a picture of a U.S. F-15 fighter "intercepting" a Russian Tu-95 "Bear" bomber off the Pacific island.

JUST WATCHED Russia's president annexes ... words Replay More Videos ... MUST WATCH Russia's president annexes ... words 01:41

JUST WATCHED Heavy clashes reported in Ukraine Replay More Videos ... MUST WATCH Heavy clashes reported in Ukraine 02:06

JUST WATCHED Analysis: Putin has already gone too far Replay More Videos ... MUST WATCH Analysis: Putin has already gone too far 03:30

JUST WATCHED Pro-Russian militants gain ground Replay More Videos ... MUST WATCH Pro-Russian militants gain ground 02:26

Guam is home to Andersen Air Force Base, which has been used by the U.S. military for flights of B-2 and B-52 bombers across the Pacific.

Flights around Japan and the Korean peninsula have also "increased drastically," as well as naval activity in that area, Carlisle said.

The Russian planes have stayed in international airspace, and such flights are not unusual, but the increase has U.S. commanders keeping a wary eye.

"It's to demonstrate their capability to do it; it's to gather intel" from U.S. military exercises with allies in the region, Carlisle said of the reasons for the Russian activity.

"We relate a lot of that to what's going on in the Ukraine," he said.

Pro-Russian separatists have taken control over swaths of Ukraine near its borders with Russia.

Ukraine's government and many in the West believe that the separatists are backed by Russia and fear that Russian President Vladimir Putin is fomenting trouble to increase his influence in the region.

Unrest has simmered in Ukraine since street protests forced out pro-Moscow President Viktor Yanukovych in February. The interim government scheduled presidential elections this month, but pro-Russian activists in the eastern part of the country refuse to accept Kiev's authority.

Russia annexed Crimea from Ukraine this year after sending troops into the region.

Since the Ukraine crisis began, the U.S. and its NATO allies have moved some troops, aircraft and ships closer to the area as a signal of alliance solidarity.