Ukrainian former parliamentary speaker Andriy Parubiy was shot dead in the western city of Lviv on Saturday and a search was under way for the killer.
The Prosecutor General's office said a gunman had fired several shots at Parubiy, killing him on the spot. The attacker fled and a manhunt was launched, it said, Reuters reported.
Parubiy, 54, was a member of parliament, had been parliamentary speaker from April 2016 to August 2019, and was one of the leaders of protests in 2013-14 calling for closer ties with the European Union.
He was also secretary of Ukraine's National Security and Defense Council from February to August 2014, a period when fighting began in eastern Ukraine and Russia annexed the Crimea peninsula.
Officials gave no immediate indication whether the murder had any direct link to Russia's war in Ukraine.
"Minister of Internal Affairs Ihor Klymenko and Prosecutor General Ruslan Kravchenko have just reported on the first known circumstances of a horrific murder in Lviv. Andriy Parubiy has been killed," President Volodymyr Zelenskiy wrote on X.
He sent his condolence to Parubiy's family and loved ones, and added: "All necessary forces and means are engaged in the investigation and search for the killer."
National police said the shooting in Lviv was reported at around noon (0900 GMT). Lviv Mayor Andriy Sadovyi said finding the killer and establishing the circumstances of the attack was of outmost importance.
"This is a matter of security in a country at war, where, as we can see, there are no completely safe places," he wrote on Telegram.
TRIBUTES POUR IN
Tributes poured in from colleagues in parliament and the government, praising Parubiy's contribution to Ukraine's fight for sovereignty and independence as one of the leaders of what became known as the Euromaidan protests in 2013-14.
Former President Petro Poroshenko said on Telegram that the killing of Parubiy, who was a member of the parliamentary committee on national security, defense and intelligence, was "a shot fired at the heart of Ukraine."
"Andriy was a great man and a true friend. That is why they take revenge, that is what they are afraid of," he said, lauding Parubiy's contribution to building out the Ukrainian army.
In a statement on Telegram, Foreign Minister Andrii Sybiha described Parubiy as "a patriot and statesman who made an enormous contribution to the defense of Ukraine's freedom, independence and sovereignty. He was a man who rightfully belongs in the history books."
Ukrainian law enforcement provided no information on the killer's identity or motives.
Ukrainian Prime Minister Yulia Svyrydenko called for a prompt investigation of the murder, calling it "a profound loss" for the country.
"You always remained a patriot of Ukraine and made a great contribution to the formation of our state," she wrote on X.
