The crisis in Ukraine showed no signs of cooling Friday. Harsh rhetoric was flying:

-- "Ukrainian Prime Minister Arseny Yatseniuk accused Russia on Friday of wanting to start World War III by occupying Ukraine 'militarily and politically,' " Reuters reports.

-- "The West wants — and this is how it all began — to seize control of Ukraine because of their own political ambitions, not in the interests of the Ukrainian people," Russian Foreign Minister Sergey Lavrov charged, according to The Associated Press.

Those sharp words followed this allegation Thursday by U.S. Secretary of State John Kerry, who accused Russia of doing nothing to help implement last week's plan to calm tensions in Ukraine: "For seven days, Russia has refused to take a single concrete step in the right direction."

Kerry also renewed the charge that Russia is funding, coordinating and fueling the armed separatist movement in eastern Ukraine, NPR's Michele Kelemen reports.

On Friday, Lavrov criticized what he says was Kerry's "unacceptable, accusatory tone."

The U.S. may move to increase sanctions on Russia and individuals close to its president, Vladimir Putin. President Obama said this week that new economic sanctions are "teed up" if Russia doesn't begin to cooperate on resolving the crisis.

Meanwhile, the BBC reports that:

"Moscow has tens of thousands of troops along its side of the border, and on Friday the acting Ukrainian Defense Minister Mikhail Koval told the Interfax-Ukraine agency that they had come within a kilometer of the border. ... Pro-Russian separatists are occupying key buildings in a dozen eastern Ukrainian towns, defying the central government."

And in eastern Ukraine, government forces have relaunched an effort to root out those pro-Russian elements, correspondent Jessica Golloher tells our Newscast Desk. That brought more harsh words from Lavrov, who accused Ukraine of waging war on its own people.

For much more on how the crisis in Ukraine has unfolded, see our earlier posts.

Update at 7:13 p.m. ET. More Escalation:

As the day has progressed, there has been more escalation. For example:

-- Interfax Ukraine reports that a pro-Russian sniper fired a shot at parked Ukrainian military helicopter, resulting in an explosion. The captain of the helicopter was injured.

-- Col. Steven H. Warren, a Pentagon spokesman, said Russian aircraft have entered Ukrainian airspace several times in the past 24 hours.

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