He said 13 Ukrainian soldiers had been wounded and one soldier killed in an attack on their military convoy as it made its way to the fighting from the main military base at Izyum, a town farther north. He said the fighting was concentrated around the cities of Kramatorsk, Semyonovka and Slovyansk.

The leader of the pro-Russian Luhansk People’s Republic, Valery Bolotov, said that he had given the border guards until evening to surrender, and that if they did not, “we will wipe them off the face of the earth.”

A border guard inside the complex, reached by telephone, who gave his name only as Nikolai, said many of the approximately 150 guards inside wanted to go back to their families, but so far their commander was not allowing them to surrender.

“I feel sorry for them,” said Lyudmila Ivanovna, a worker from a veterans’ union who was trying to negotiate their release. “We’re trying to talk to the commander, but he’s not agreeing to speak.”

On Tuesday afternoon, the weedy area around the mustard-colored complex was windy and deserted, and bullet holes riddled the walls. Passers-by were touching bullet holes in a wall of one of the apartment buildings.

In Luhansk, new information on an explosion at the regional administration building on Monday that killed eight people pointed to fire from an aircraft as the culprit. Mr. Bolotov said an analysis of the pieces of shrapnel and rocket casings showed they were from an S-8 rocket that is typically shot from an SU-25 fighter jet.

A long string of at least 13 large holes had been torn into the ground, forming a raw line from a small park near a jungle gym to the front of the building, where a fourth-floor window and wall had been blown out. The Ukrainian military has denied responsibility for the attack, which seemed to harden even those residents inclined to think the best of the Kiev government.