MARYINKA, Ukraine — Though overshadowed by the war in Syria, fighting in eastern Ukraine has picked up sharply in recent weeks, residents along the front line, commanders and European monitors say.

The resumption of hostilities in Ukraine, with exchanges of machine gun and mortar fire across the front line up to levels not seen since last summer, suggests a willingness by Russia, which supports the rebels in eastern Ukraine, to sustain two conflicts at once. In late September, Russia began airstrikes in Syria on behalf of the government of President Bashar al-Assad.

A cease-fire took hold here in eastern Ukraine between Russian-backed separatists and the government on Sept. 1, which was apparently coordinated with Russia’s military deployment in Syria.

But that truce is now unraveling, and Maryinka has become one of the new hot spots.

“A week ago, we had shelling every two to three days, and mostly at night,” Lt. Col. Mikhailo M. Prokopiv, the commander of Ukrainian Army troops in this town, said in an interview on Sunday while touring the front line. “Now, not a day goes by when we don’t fight.”