A Ukrainian military spokesman says a one-day truce announced by the president will serve as a test for the prospects of a definitive cessation of hostilities against Russian-backed separatists.

President Petro Poroshenko's declaration on Thursday of a break in the fighting in eastern Ukraine marks a new attempt to revive a September cease-fire deal that has been violated almost daily.

Spokesman Andriy Lysenko said Friday the "day of silence" to be held Tuesday would demonstrate the degree of coordination within rebel forces.

Despite multiple initiatives, fighting remains intense in eastern Ukraine. Lysenko said Friday that six Ukrainian soldiers had died in the previous day's combat.

The U.N. says more than 4,300 people have been killed since the conflict began in mid-April.