A mob spearheaded by around 30 men carrying Kalashnikov assault rifles and grenade-launchers attacked the regional police headquarters in Lugansk, raising the heat in the worst East-West confrontation since the Cold War.
They had earlier seized the regional prosecutors' office, tearing down the Ukrainian flag and replacing it with that of Russia, which the West blames for stoking the violence in the ex-Soviet Republic.
More than a dozen towns and cities in the east have now fallen to pro-Russian rebels, who see the Western-backed leaders in Kiev as illegitimate "fascists" and want either independence or outright accession to Russia.
"It's good what the young people are doing. We don't want this Nazi junta that has seized power in Kiev. We don't recognise them. I want my children and grand-children to grow up in Russia," one retired engineer told AFP as he surveyed the violence in Lugansk.
As police failed to quell the violence and in some cases stood by, interim president Oleksandr Turchynov lashed out at what he called "inaction" and in some case "treachery" by law enforcement bodies on the ground.
He urged "Ukrainian patriots" in the region to sign up for police duty to counter the pro-Moscow insurgency that threatens to tear his country apart.
The latest unrest in Lugansk followed yesterday's terrifying scenes in nearby Donetsk, where pro-Russian thugs armed with baseball bats, knives and fireworks attacked a pro-Ukrainian demonstration, wounding several in what Washington's ambassador to Ukraine called "terrorism, pure and simple".
As the situation on the ground descended further into chaos, the war of words between Moscow and the West continued, with Russia saying the United States was resorting to "Iron Curtain" policies with its new sanctions unveiled yesterday.