Ukraine moves to retake rebel-held Slavyansk

A pro-Russian separatist guards a checkpoint as tires burn behind him near the town of Slavyansk in eastern Ukraine, May 2, 2014.

Ukraine launched a "large-scale operation" to retake the eastern city on Friday, in an escalation of violence in what has become the worst confrontation between Russia and the West since the Cold War.

Slaviansk, Ukraine

A pro-Russian armed man guards a checkpoint, May 1, 2014.

Slaviansk, Ukraine

A pro-Russian separatist guards a checkpoint while walking near burning tires, May 2, 2014.

Slaviansk, Ukraine

A Ukrainian military helicopter lands near a Ukrainian checkpoint, May 2, 2014.

Slaviansk, Ukraine

A woman stands with an Orthodox icon at a Ukrainian checkpoint, May 2, 2014.

Slaviansk, Ukraine

Ukrainian soldiers stand guard at a Ukrainian checkpoint, May 2, 2014.

Slaviansk, Ukraine

A man shakes hands with Ukrainian troops at a checkpoint, May 2, 2014.

Slaviansk, Ukraine

Civilians talk with Ukrainian troops, May 2, 2014.

Slaviansk, Ukraine

A pro-Russian separatist guards a checkpoint as tires burn behind him, May 2, 2014.

Slaviansk, Ukraine

Pro-Russian separatists guard a checkpoint, May 2, 2014.

Slaviansk, Ukraine

A pro-Russian separatist guards a checkpoint as tires burn in front of him, May 2, 2014.

Slaviansk, Ukraine

A pro-Russian separatist stands guard on top of an armored personnel carrier, May 2, 2014.

Slaviansk, Ukraine

A Ukrainian soldier stands guard on railway tracks, May 2, 2014.

Slaviansk, Ukraine

Ukrainian soldiers stand guard at a Ukrainian checkpoint, May 2, 2014.

Slaviansk, Ukraine

Pro-Russian men watch as a woman enters the mayor's office, May 1, 2014.

Luhansk, Ukraine

A boy with a toy gun walks in front of seized regional government headquarters, May 2, 2014.

Slaviansk, Ukraine

A pro-Russian separatist shows Ukrainian bullet casings at a pro-Russian checkpoint, May 2, 2014.