Ukrainian President Petro Poroshenko is demanding police find and punish the killers of anti-corruption activist Kateryna Handziuk.
Handziuk died Sunday, three months after she was severely burned in an acid attack.
She underwent 11 operations after the attack.
"I want to address the law enforcement bodies so that they do everything possible to find the murderers, to punish them, and put them on the defendants' bench," Poroshenko said shortly after getting the news of Handziuk's death.
Police have the alleged attacker in custody, but they still do not know who ordered the attack.
Ukrainian Prosecutor General Yuriy Lutsenko initially said the attack was the work of separatists, but the investigation continues.
The 33 year-old Handziuk was a senior official and anti-corruption activist in the major southern port of Kherson.
Hundreds gathered outside the interior ministry in Kiyv Sunday in her memory.