* Vote organised on ad hoc basis, ballot paper confusion
* West fears slide into civil war
* Streets in rebel cities barricaded with felled trees, tyres
MARIUPOL/SLAVIANSK, Ukraine, May 11 (Reuters) - Pro-Russian separatist leaders pressed a referendum on self-rule across eastern Ukraine on Sunday that has raised fears in Kiev and the West of civil war and dismemberment.
Clashes flared anew on the outskirts of Slaviansk, the most heavily defended rebel redoubt, as the first voters appeared at polling stations, making their way through streets criss-crossed with barricades of felled trees, tyres and rusty machinery.
"I wanted to come as early as I could. We all want to live in our own country," said Zhenya Denyesh, a 20-year-old student voting at a three-storey concrete and glass university building.
Asked what he thought would come after the vote, he replied: "It will still be war."
Ukrainian leader Oleksander Turchinov told pro-Russian eastern regions on Saturday that if they move to secession it would be taking a step into the abyss. He said such a move would destroy the economy of the region, that produces 16 percent of Ukraine's GDP.
Kiev and the West accuse Moscow of engineering the crisis, portraying the Ukrainian government as a body hostage to militant anti-Russian nationalists, and backing the rebel fighters with special forces, an allegation Moscow denies.
Kiev authorities consider the referendum illegal.
(Writing by Ralph Boulton; Editing by Aleksandar Vasovic)