Ukrainian separatist rebels are reporting “heavy losses” today as the nation’s military attacks the key Donetsk Oblast town of Krasny Liman, along with several neighboring villages.

Details are scarce on the fighting, but the rebels report 20 Ukrainian tanks along with other armored vehicles attacking the town. The rebels claimed to have destroyed a single tank and have so far prevented an advance into the town.

Ukraine’s military told the rebels they had “three hours” to unilaterally disarm, and attacked when they refused. The military has since been dropping leaflets on Krasny Liman that read “You will all be destroyed! There will be no further warnings,” along with separate leaflets ordering all civilians to leave town immediately.

The rebels continue to call for Russian aid in the face of the offensive, and NATO today claimed Russia has been deploying troops close to the border again. Russia has warned Ukraine it won’t stand by while the Ukrainian military attacks the ethnic Russian easterners, and the two sides have been talking about a ceasefire, though so far it hasn’t materialized on either side.