WASHINGTON — Russia is locking down control of Crimea before Sunday’s referendum on splitting from Ukraine — even burying deadly land mines to deter an unlikely counterinvasion.

Forces loyal to Moscow planted mines in the Kherson region, just north of the Crimean border, and began to install border markers between the two regions.

The Russian forces are “setting up mine fields across the narrow strip of land that connects Ukraine with Crimea” in an apparent effort to block Ukrainian forces from entering, Alexei Mazepa, the regional spokesman for the Ukrainian Defense Ministry, told the LA Times.

In other developments in the Cold War-style standoff: