MOSCOW (AP) — A Ukrainian baritone who performed in French opera productions for nearly two decades before joining a volunteer battalion in warring eastern Ukraine has been killed in the fighting.

Ukrainian news reports cited the nationalist group Pravy Sektor as saying Wassyl Slipak was killed on Wednesday by a sniper.

The reports said Slipak had abandoned his singing career two years ago to join the fight of Ukrainian soldiers and volunteers against Russia-backed rebels. Nearly 9,500 people have been killed in the conflict, according to U.N. figures.

Slipak had performed at the Paris National Opera and productions throughout France, according to his webpage.

Under the cease-fire agreement reached last year in Minsk, the Belarusian capital, both the separatists and Ukrainian government forces pledged to pull back heavy weaponry as well as take other steps toward a peace settlement.

In a statement on Wednesday, Ivan Simonovic, head of the U.N. Human Rights chief's office in New York, said the death toll of early 9,500 includes up to 2,000 civilians.

Simonovic said in the past month "half of all civilian casualties were caused by shelling from mortars and howitzers - weapons which use in the conflict zone are prohibited by the Minsk Agreements."

Simonovic warned of a possible "re-escalation of wide-scale hostilities if urgent action is not taken to separate sides and remove heavy weaponry."