Ukraine military checkpoints in the troubled eastern region have been threatened with attack unless they are withdrawn on Thursday night.
A senior rebel commander issued the ultimatum in a video posted on a social media website.
The eastern uprising by pro-Russian separatists has show no sign of relenting. Confrontations between militants and Ukraine troops are continuing with the rebels taking every possible opportunity to remove all signs of support for Kyiv.
There has been no indication from the government that the ultimatum will be respected as it too is staging so-called “special anti-terrorist strikes”.
Interim President Oleksandr Turchynov told parliament that as part of the operation a hidden rebel base near Kramatorsk was discovered and destroyed.
The government also insisted it would not put off plans to hold the presidential election on May 25.
Some eastern regions have stated they will not take part while others say the pro-Russian rebellion risks undermining the results.