Rebel commander Alexei Mozgovoi killed in Ukraine

Alexei Mozgovoi, one of the top separatist commanders in eastern Ukraine, has been killed in an attack on his car on Saturday, rebel authorities announced.

The defence ministry, and Russian and Ukrainian media confirmed Alexey Mozgovoi and six other fighters were killed in the attack after a bomb struck the car they were travelling in before a gunfight ensued.

The incident happened around 3pm GMT near the town of Alchevsk, some 40 kilometres from Lugansk, the official press agency of the self-declared republic said in a statement.

Mozgovoi was a commander of a police battalion in the war-torn region and as a critic of the Russian-backed separatist leadership and the Minsk accord signed with Kiev.

He took control of Alchevsk as part of the uprising that began last April in eastern Ukraine's Luhansk and Donetsk regions following Russia's annexation of Crimea.

 “According to the preliminary information, the vehicle carrying Mozgovoy was hit by a bomb and then by machine-gun fire,” it said.

“There are seven dead in total,” deputy Lugansk prosecutor Sergei Gorenko said at a press conference broadcast by Russian media, though he stressed that the toll was based on early information and could still change.

“One of the lines of inquiry is that it was an act of sabotage by a group of spies,” he added.

Mozgovoy was the well-known leader of the so-called Prizrak (Ghost) brigade that has taken part in some of the heaviest battles in Ukraine’s pro-Russian east since the start of the conflict last year.

In December, the United States added his name to a list of people subject to sanctions for their involvement in the crisis, which has left more than 6,200 people dead so far.

In February, the insk ceasefire agreement came into effect on 15 February, but there has been regular sporadic fighting and both the pro-Russian separatists and the Ukrainian government accuse the other of preparing a major offensive.

The Ukrainian government and Western leaders say there is clear evidence Russia is helping the rebels with heavy weapons and soldiers - an accusation Moscow denies.

But the rebels are also not a single coherent force in eastern Ukraine and there have been reports of power struggles.