MARIUPOL, Ukraine - As two of the most tense regions in eastern Ukraine prepare to vote on declaring sovereignty, the country's acting president is warning them against self-destruction.

Sunday's ballots seek approval for declaring so-called sovereign people's republics in the Donetsk and Luhansk regions, where pro-Russia insurgents have seized government buildings and clashed with police and Ukrainian troops.

At least seven people died Friday in clashes in the city of Mariupol. The city remained on edge Saturday, with barricades of tires blocking some streets in the city's center.

The referendums are being conducted by the insurgent movements and are not regarded as legitimate by Kiev or the West. The elections chief of the insurgents in Donetsk, Roman Lyagin, was quoted by news agencies as saying voting in Mariupol and one other district had begun early because of rising tensions there. He did not elaborate.

Ukrainian President Oleksandr Turchynov, in comments posted on the presidential website Saturday, said supporters of independence for the east "don't understand that this would be a complete destruction of the economy, social programs and general life for the majority of the population."

"This is a step into the abyss for the regions," he said.

The hastily arranged referendums are similar to the March referendum in Crimea that approved secession from Ukraine. Crimea was formally annexed by Russia days later.

But organizers of the eastern vote have said that only later will a decision be made on whether they would use their nominal sovereignty to seek full independence, absorption by Russia, or to stay part of Ukraine but with expanded power for the regions.

Turchynov and Ukraine's interim government came to power in February after the ouster of Russia-friendly president Viktor Yanukovych following months of protests in Kiev.