Blood flowing from a bullet wound, the grey-haired man lies in the middle of the roadblock waving weakly for help as shots ring out nearby and thick black smoke from burning tyres curls into the sky.

"I've called an ambulance. They have to come, they have to come," a man screams, ducking for cover behind a concrete breezeblock.

A hundred metres (yards) away, a column of Ukrainian army armoured vehicles opens fire again. The sound of their mounted machine guns and the soldiers' automatic rifles echoes as they move in on one of the remaining pro-Russian rebel checkpoints just south of the rebel bastion of Slavyansk.

From nearby trees, separatist gunmen shoot back with the clack-clack-clack of sporadic automatic gunfire.

They are retreating, as they realise they are no match for the larger Ukrainian force.

A grey sedan car on the road sits immobile, pointing away from the fighting. Its windows are shot out. Inside a driver writhes in pain while a man tries to wrap a tourniquet around his arm before diving to the verge as more shots are fired.

Lying sprawled on the road by the car is the body of a middle-aged man. His back is riddled with bullet holes. His beige jacket is seeped in blood. A man tries to drag him to the side of the road.

"Come here, film this!" two women tending to the man shout to me and the AFPTV camerawoman with me.

Meanwhile, two armed separatists holding automatic rifles crouch behind a tree. They yell at a group of civilians to get out of the area as quickly as possible.

- 'Who's shooting?' -

Not very far away, on the outskirts of the town of Kramatorsk -- the last town to the south of Slavyansk on the road from the regional capital Donetsk -- the rebels are in control.

A handful of masked men crouch behind a van with rifles as a small pile of tyres burn in the road.

Other militants gather Molotov cocktails by the side of the road while onlookers warily peer in the distance at the smoking checkpoint.

"What's going on? Who's shooting -- us or them?" asks one man hiding in a bus stop and clutching a beer. By "them" he means the soldiers.

After about half an hour the sound of firing subsides. Two ambulances drive at speed through Kramatorsk with their sirens wailing.

The Ukrainian soldiers have taken control of the checkpoint.

It's a small victory for the military on the second day of an operation against the rebels in Slavyansk.

But it's short-lived.

Less than two hours later, the Ukrainian soldiers who had fought so hard to take the checkpoint abandon it. It's not clear why.

Angry local residents wander around the smouldering wreckage. A few cars nervously pass through, past two empty petrol tankers the rebels had been using as barriers. The ends of the tankers are shorn off, apparently by heavy weapon fire or from an explosion.

"They drove off through the fields," pensioner Fyodor Mordiltsev said.

"The authorities in Kiev don't care about their people. They have sold out to the White House".