JARAK, Serbia, (Reuters) - Serbian police blocked all roads leading to an ethnically mixed village north-west of Belgrade to prevent an ultranationalist leader, convicted for crimes against humanity during the 1990s wars, from holding a rally there.

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Vojislav Seselj had planned a rally in the village of Hrtkovci to mark 26 years since his speech there which the United Nations war crimes judges identified as a crime against humanity for “instigating deportation and persecution.”

One protester from a rival group was slightly injured in a brawl with Seselj supporters in a nearby village before police stepped in to prevent further clashes.

Serbian police had banned the rally which would have unnerved the remaining Croat minority in the village of Hrtkovci.

Most of the Croat population left the village during the conflicts of the 1990s. Before the break up of former Yugoslavia Croats accounted for 40 percent of the population in there compared to 10 percent now.

On Sunday morning police had put road blocks in the neighboring village of Jarak and did not allow anyone to move to Hrtkovci.

Seselj and dozens of his supporters were stopped at the road block in Jarak. They came out of buses and waved Serbian flags.

“We wanted to have a peaceful rally, and the regime had banned it without any reason,” Seselj told reporters.

But as he was leaving supporters of the Liberal Democratic Party (LDP) arrived and held a banner reading “Seselj is a war criminal,” sparking skirmishes.

Seselj founded the Serbian Radical Party and was deputy prime minister under Slobodan Milosevic during the wars that accompanied the breakup of Yugoslavia in the early 1990s in which more than 100,000 people were killed.

Both the LDP and the Serbian Radical Party are opposition groups in Serbia.