MARIUPOL, Ukraine — Wearing camouflage, with a bushy salt-and-pepper beard flowing over his chest and a bowie knife sheathed prominently in his belt, the man cut a fearsome figure in the nearly empty restaurant. Waiters hovered apprehensively near the kitchen, and try as he might, the man who calls himself “Muslim,” a former Chechen warlord, could not wave them over for more tea.

Even for Ukrainians hardened by more than a year of war here against Russian-backed separatists, the appearance of Islamic combatants, mostly Chechens, in towns near the front lines comes as something of a surprise — and for many of the Ukrainians, a welcome one.

“We like to fight the Russians,” said the Chechen, who refused to give his real name. “We always fight the Russians.”

He commands one of three volunteer Islamic battalions out of about 30 volunteer units in total fighting now in eastern Ukraine. The Islamic battalions are deployed to the hottest zones, which is why the Chechen was here.