Ukrainian security forces have been tightening the ring around Donetsk, and the number of clashes has increased in recent days.

That was brought home to us Friday morning when fighting broke out shortly after 5 a.m. at a rebel-controlled checkpoint about six miles beyond the city limits.

A pro-Russian rebel we talked to said four militants in his unit were killed when pro-Ukrainian fighters attacked the checkpoint,  located at the foot of a narrow bridge at the Karlovskoye reservoir. The rebel said at least 10 pro-Ukrainian fighters were also killed, a claim that could not be immediately verified.

A pro-Russian rebel stands near body of man he said was ultra-nationalist Ukrainian after attack on checkpoint outside Donetsk. (Fredrick Kunkle/The Washington Post)

A pro-Russian rebel stands near the body of man he said was an ultra-nationalist Ukrainian after attack on a checkpoint outside Donetsk. (By Fredrick Kunkle/The Washington Post)

The body seen lying behind him in the photo above was that of a right-wing ultra-nationalist Pravy Sektor fighter who had been killed in the fighting, the rebel said.

"This is the first person who shot at us," the rebel said. "The others ran away."

The body had been moved from the site of the fighting to this spot, a new checkpoint where the pro-Russian rebels had fallen back, and they were waiting for an ambulance to retrieve the victim. The rebel would not identify himself other than as a spokesman and would not let us take a picture of him except from the neck down. He was wearing a balaclava and the orange-and-black striped St. George ribbon, which was a Russian military decoration with high honors introduced in the days of Catherine the Great.

Farther north, at the site of the shootout, a large restaurant with holes in it from some sort of heavy explosive was still smoldering. Shell casings littered the ground around a nearby gas station and a small onion-domed church. The checkpoint had been abandoned by both sides. Inside one of the fortifications were bloodstains and about a dozen Molotov cocktails that the occupants had not been able to use.

"It was horrible," said Alla Nikolenko, 45, who owns a small grocery store near where the fighting occurred. She said the shooting started about 5:20 a.m. and continued for about five hours. A shell narrowly missed her home but damaged a window.

"We never thought we would see this in our lives," she said, her eyes filling with tears.

The violence occurred two days after one of the most deadly clashes since the conflict began when 16 people were killed late Wednesday in the town of Volnovakha about 18 miles south of Donetsk