Things are moving very quickly in Ukraine. Here's what has happened since 11 a.m. ET.
Pro-Russian leader arrested
Ukrainian authorities arrested the leader of a pro-Russian movement in the eastern city of Donetsk, the Security Service of Ukraine said Thursday in a prepared statement. The service said it detained Ukrainian national Pavlo Gubarev, the self-proclaimed governor of Donetsk. The arrest took place in Gubarev's apartment after a court order, the Security Service said.
U.S.: Crimean referendum unconstitutional
The proposed referendum in Crimea would violate the Ukrainian Constitution, as well as its sovereignty and international law, Deputy National Security Adviser Ben Rhodes said via Twitter on Thursday. Ukraine's government must be "involved in any decisions about the future of Crimea or any part of Ukraine," Rhodes said.
U.S. beefing up military assets
The Defense Department says six F-15s have arrived in Lithuania as part of the measures that U.S. Defense Secretary Chuck Hagel announced Wednesday.
Bush-era envoy: Putin has strategy, Obama doesn't
John Bolton, former U.S. ambassador to the U.N. who is now a senior fellow at the American Enterprise Institute, weighed in on how the Obama administration is handling Ukraine in his remarks at the Conservative Political Action Conference.
"We're not going to get peace through strength because we're not devoting the budget to it," he said. "But we're not going to get peace through weakness either. We're gonna get what we see today in the Ukraine where Vladimir Putin has a strategy and Obama has nothing, where Putin has a growing defense budget, and ours is shrinking."