KIEV - A Ukrainian National Guard officer died on Monday after being injured in the heart in fierce clashes between protesters and police that wounded around 100 people.
"He died on the operating table," a spokeswoman for the National Guard, Svitlana Pavlovska, told AFP.
Street battles broke out between dozens of demonstrators and police outside parliament as MPs backed on first reading controversial constitutional amendments giving more autonomy to pro-Russian separatists.
It was worst unrest in Kiev since a bloody popular uprising ousted Kremlin-backed Viktor Yanukovych early last year.
Around 100 people were injured on Monday including around 90 police, with authorities detaining some 30 people.
Interior ministry advisor Anton Gerashchenko said the guardsman who died was a conscript.
Interior Minister Arsen Avakov initially said the officer, who is believed to be 24 or 25, died from a bullet wound to the heart but later wrote that he was apparently killed by a fragment of a grenade.
"More than 30 people have already been detained. More to come," Avakov said on Facebook, adding that people who threw "several" explosive devices wore T-shirts with the logo of the Svoboda nationalist party.
Avakov said the protester who had thrown the grenade had been also detained.
He said the authorities had confiscated several grenades including an F-1 grenade which Avakov noted had a maximum radius to cause death and injury.
"Investigation and punishment will be unavoidable," he said, calling the clashes an "anti-Ukrainian war".
Oksana Blyshchyk, a spokeswoman for Kiev police, said separately that around 100 police were injured including 10 in critical condition.
French journalist Antoine Delaunay wrote on Twitter that he "took a rock" to his face.
At least one photographer was also lightly injured.