The unwillingness of security structures to defend public buildings from separatist occupation has been a theme in eastern Ukraine since early April. Supporters of the "Donetsk People's Republic" have taken over a string of city halls and police stations. An armed unit from Crimea - led by an alleged Russian colonel - has also established a de facto military capital in the town of Slavyansk.

But in recent days Kiev's tentative grip on local law enforcement in the east appears to have slipped completely. In Luhansk riot police stood passively in a courtyard, kettled in by separatists armed with bats and hammers. "The regional leadership does not control its police force," Stanislav Rechynsky, an aide to the interior minister in Kiev, told Reuters. "The local police did nothing."

In a statement on Tuesday, Ukraine's interim president, Oleksandr Turchynov, said: "The vast majority of law enforcement officials in the east are not able to fulfil their obligation to protect our citizens."