KIEV (AFP) Ukraine on Saturday marks the 300th anniversary of a key battle fought on its soil between imperial Russia and Sweden, with the role of a Cossack commander providing a new source for Russia-Ukraine acrimony.

The Battle of Poltava -- fought on June 27, 1709 near a town by that name in central Ukraine -- is seen as the pivotal victory for Russia in its two-decade struggle with Swedish King Charles XII.

It was recorded in Soviet-era text books as the moment Russia -- under Peter the Great -- replaced Sweden as the dominant power in Eastern Europe.

But amid the great power clash, the role of one Ukrainian commander, Ivan Mazepa, is providing fuel to the debate about Kiev's allegiances in the tug-of-war between the country's pro-Western and pro-Russian politicians.

The Ukrainian Cossack leader -- a nationalist reformer who appears on the country's 10-hryvnia notes -- is remembered as a traitor by Moscow loyalists but a hero by Ukraine's Western-leaning nationalists.

Mazepa -- while formally allied with Peter the Great -- switched sides and fought alongside Swedish forces, allegedly angered by Russian incursion on Ukraine's autonomy and the Tsar's failure to protect it against Polish attacks.

Ukrainian President Viktor Yushchenko slammed as "prolonged hysteria" this year Russian accusations of Mazepa's "so-called betrayal" and created a new national award in the name of the controversial hero.

"Ivan Mazepa is not a traitor since he did not betray the Ukrainian people," Yushchenko said. "He had only one goal: to preserve the independence of the Ukrainian state."

But the president's pro-Russian opponents hit back.

"Yushchenko glorifies such figures to make an enemy out of Russia and we will not allow this," said Valery Konovalyuk, a lawmaker with Ukraine's Party of the Regions.

"With the help of intrigues and betrayals, Mazepa angled for his personal independence and not that of the Ukrainian people."

Meanwhile, the Ukrainian People's Party complained that the mayor of Poltava had banned it from marching to commemorate Ukrainian Cossacks who died in the battle, while approving a religious procession in the name of Russian victory.