While the world was watching the aftermath of the downing of Malaysia Airlines Flight 17, Ukraine stepped up its fight against the separatists, firing on rebel positions in areas of the northwest of the city. Ukraine denied it had hit civilian areas. But at least three of the approximately seven blast sites had trajectories and impact damage consistent with a rocket’s being fired from the northwest, where the Ukrainians are based.

“I hate them all,” said an elderly woman, whose front yard had been swallowed up by a large crater. She was sweeping glass off her windowsill in orange gloves, and trying to salvage some old photographs that had been torn. “I don’t know who did this. But let him come, and have his child and his loved ones end up in this situation.”

A Ukrainian military spokesman, Vladislav Seleznyov, would not provide details, citing military secrecy, but confirmed the fighting, calling it “an active phase of the antiterrorist operation.”

A spokesman for Ukraine’s National Security and Defense Council, Andriy Lysenko, confirmed that government forces were closing in on Donetsk and Horlivka, another rebel stronghold.

Mr. Lysenko denied, however, that government troops had fired any mortars at Donetsk — the government’s standard position — even though heavy fighting in the city cast doubt on his assertion.