Many people in Donetsk believe fascists seized control of Ukraine's government during the revolution in February. They argue that only independence and Russia's protection can guard against this threat.
The announced result seemed suitably Soviet: Ninety per cent of voters were in favour of sovereignty, pro-Russian insurgents said.
Roman Lyagin, election chief of the "Donetsk People's Republic", said around 75 per cent of the region's eligible voters cast ballots, and the vast majority backed self-rule.
With no international election monitors in place, it was all but impossible to verify the claims. The preliminary count was announced just two hours after the polls closed. No immediate results were released for the second referendum in the Luhansk region.
Although the voting appeared mostly peaceful, armed men identified as members of the Ukrainian national guard opened fire on a crowd outside the town hall in Krasnoarmeisk, and an official with the region's insurgents said people were killed. The bloodshed took place hours after dozens of armed men shut down voting.
Watch: Pro-Russia insurgents to Vote
Olga Velichko had been queuing for two hours to vote in Mariupol. "We are longing for change," she said. "We consider the referendum an opportunity to show our anger and hatred of the Kiev Government."
Polling stations in Mariupol, the second biggest city in Donetsk, were besieged by voters, with one queue stretching half a kilometre down the street. It was impossible to find anyone planning to vote "no".
Ukraine's security forces have infuriated many of Mariupol's people with a series of heavy-handed operations. Last week, they killed at least five and perhaps 20 people in the city, before effectively surrendering the streets to pro-Russians.
Locals believe innocent civilians were the main victims of that attack, which they refer to as "May 9".
"What we have seen here is fascism in its true meaning," said Galina Kovalenko, who had waited for hours to vote. "Those who were undecided before May 9, now they have made up their minds."
- additional reporting AP