The press service for the separatist Luhansk territory in eastern Ukraine (LITs) reported on Saturday a top rebel commander and six other rebel soldiers were killed in an attack by an unknown group of assailants.
The leader of the rebel “Ghost” battalion Aleksey Mozgovoi was travelling as his car was blown up by explosive device and then came under machine gun fire, said separatist spokesman Sergei Gorenko.
Gorenko didn’t give further details about the incident, or named the other six killed in the attack which took place at the town of Alchevsk, about 30 km eastern of the frontline.
"At the moment, one theory is that it was the work of a raiding group," said Gorenko.
Clashes between the Russian-backed separatists and Ukrainian troops have claimed more than 6,200 lives and caused more than 1 million people to flee their homes.
Russia and Ukraine have been at loggerheads ever since months of pro-EU demonstrations in Kiev forced former pro-Russian leader Viktor Yanukovych to flee the country in February 2014.
The political crisis led the autonomous government in Crimea, which is dominated by ethnic Russians, to declare independence from Ukraine and eventually be annexed by Russia following a referendum a month later.
Russia’s annexation of Crimea and aggression in eastern Ukraine caused its relations with the United States and the European Union to reach their worst since the end of the Cold War era.
The West accuses Russia of supporting the separatists groups in eastern Ukraine, providing them weapons, while Russia denies the claims.