(CNN) -- Bloodstained pavement, a woman's compact, a pair of shattered spectacles, a single shoe covered in dust were among the debris left by a devastating series of explosions that hit the headquarters of the pro-Russian separatists in the eastern Ukrainian city of Luhansk on Monday.
The carnage was sudden, unexpected. This was the middle of a city, a building adjacent to a leafy square, where civilians walked and worked. Eight people were killed, five women and three men, according to the self-declared Luhansk People's Republic; the authorities in Kiev reported the same tally.
But there the agreement ends.
The pro-Russian leadership in the city immediately accused the Ukrainian air force of carrying out the attack. A fighter jet had been flying overhead at the time, and social media video appeared to show it firing cannon or rockets. The authorities in Kiev denied its planes had been involved. Initially, the anti-terrorist operation said the explosion originated from inside the building, then that an anti-aircraft missile operated by the separatists had misfired, reacting to heat from an air-conditioning system on the outside of the building.
But a CNN investigation in Luhansk has found clear evidence that whatever detonations hit the building and the adjoining park came from the air. The tops of trees were splintered, and a series of small craters -- about a dozen -- had been blasted in a straight line, starting in the park and reaching the walls of the building, blowing out many of its windows and spraying the area with jagged shrapnel. That's what appears to have killed most of the victims and injured 20 more.
The pattern of the craters clearly indicated some sort of strafing, according to a munitions expert at the scene with CNN. Their size suggested 30-millimeter ordnance, he said, which is standard equipment on the Su-25, a ground attack fighter, and the Su-27 -- both combat aircraft operated by Ukraine.
The Special Monitoring Mission of the Organization for Security and Co-operation in Europe came to a similar conclusion, releasing a statement late Tuesday that said: "Based on the SMM's limited observation, these strikes were the result of non-guided rockets shot from an aircraft."
It's thought to be the first time that civilians have been killed or injured in an attack by the Ukrainian air force since pro-Russian groups began occupying buildings in the Luhansk and Donetsk regions more than two months ago.
The self-declared prime-minister of the People's Republic of Luhansk, Vasily Nikitin, told CNN he hoped the attack would spur Russian President Vladimir Putin to action.
"We appealed to Russia to send us peacekeepers. I think after they see what happened to us in the center of our town, they'll send them more quickly," he said.
Nikitin said he was ready to provide all the evidence collected to independent experts.
Nick de Larrinaga, Europe editor of IHS Jane's Defence Weekly, told CNN he believed the Ukrainian air force "used their Su-25 'Frogfoot' ground attack aircraft during the operation in Luhansk. It is specifically designed for attacking ground targets -- unlike the Su-27, which is principally a fighter aircraft."
The planes were flying to provide support for a base of the Ukrainian Border Guard on the edge of the city. Why one may have targeted the administrative building, several miles away, is unknown.
The Border Guard compound, in a southern suburb of Luhansk, came under attack before dawn Monday. It was a concerted assault from several directions, involving hundreds of pro-Russian militants, and continued for some 12 hours. On a visit to the site Tuesday, a CNN team found dozens of spent cartridges in several locations around the base, whose buildings had also been hit by rocket-propelled grenades. Part of the roof of the main building hung precariously in the strong wind. Vehicles outside had been burned out, the fuel dump blown up.
By late afternoon, only a token force of separatists were still in place, using blocks of apartments within 100 meters of the base as protection. They cradled brand new assault rifles and carried boxes of ammunition but insisted they were local men. Patches of dried blood marked the place where one of several militants killed or wounded Monday had been hit by gunfire from the base.
One of the separatists, who gave his name as Oleg, said, "They call this an anti-terror operation, but it's wrong. When they use air force against their own people, it's wrong." He dismissed Ukraine's President-elect, Petro Poroshenko, as "illegitimate."
Oleg and other fighters said the base had been attacked because it was the hub for Ukrainian patrols along a several-hundred-kilometer stretch of the nearby border with Russia -- an area that has seen increased infiltration by Russian militants and weapons in recent weeks.
Several soldiers inside the compound were also injured in the clashes, and windows in the adjoining apartment blocks were pock-marked with bullet holes.
As CNN filmed, two men raced into the base through its charred gate-house.
The battle for eastern Ukraine is intensifying. The casualties are rising, as are the number of pro-Russian separatists and the roadblocks dotted throughout the region. And in some areas, the only obvious presence of the Ukrainian state is in the sky.