1 LINKEDINCOMMENTMORE

Fear of a Russian invasion hung over eastern Ukraine on Wednesday as NATO said 20,000 combat forces massed on the border for war games could intervene under the pretext of helping ethnic Russian civilians caught up in what Moscow calls a "humanitarian catastrophe."

The concern comes as Ukrainian forces pushed toward encircling the separatist bastion of Donetsk and battled on against pro-Russian rebels in Luhansk. The renegades have declared the cities the capitals of two "people's republics."

The United Nations says that fighting between Ukrainian forces and Russian-backed separatists have forced more than 285,000 residents to flee their homes. Tuesday night, Moscow called for an emergency meeting of the U.N. Security Council to discuss the situation.

U.S. Defense Secretary Chuck Hagel on Wednesday called the Russian buildup "a threat" and said an invasion was "a possibility — absolutely."

Polish Prime Minister Donald Tusk said earlier that "the threat of a direct intervention is definitely greater than it was a few days ago, or two weeks ago."

NATO expressed "great concern" about the Russian movements.

"We share the concern that Russia could use the pretext of a humanitarian or peacekeeping mission to send troops into eastern Ukraine," spokeswoman Oana Lungescu said in an e-mailed statement.

In Moscow, a Defense Ministry spokesman said "such statements only raise sympathy for the speakers of the Pentagon, the State Department and NATO. It seems the people are serious, but they have to constantly improvise during their speeches to somehow add seriousness to their statements."

The verbal skirmishing came as Russian President Vladimir Putin announced bans on all agricultural imports from the United States in retaliation for sanctions imposed on Russian companies, banks and his close associates.

STORY:Russia to ban all U.S. agricultural imports

After Ukraine's elected president was deposed this spring, Putin annexed Ukraine's strategic Crimea Peninsula in March, and he has backed the separatist battle that ethnic Russians began in April in eastern Ukraine.

The Christian Science Monitorpointed out that Putin had massed 40,000 troops on the Ukraine border in March but did not send them across. Experts said that major military drills are typically held in August in Russia and that this week's war games are simply intended to rattle nerves.

The intensified fighting has interrupted the work of investigators gathering evidence of the Malaysian Airlines jetliner that was shot down over eastern Ukraine last month.

"The security situation is deteriorating rapidly, and our people are no longer able to do their work," Dutch Foreign Minister Frans Timmermans said Wednesday. "But we will resume the work as soon as the situation allows."

Flight MH17 was flying from from Amsterdam to Kuala Lumpur when it exploded in midair July 17, killing all 298 people on board. Western governments say evidence indicates the plane was brought down by a Russian-made missile fired from rebel-held area, but the separatists and Moscow have denied responsibility.

1 LINKEDINCOMMENTMORE
Read or Share this story: http://on.ksdk.com/1nuf9Sy