KIEV -- Former Ukrainian parliament speaker Andriy Parubiy was shot dead on Saturday in the western city of Lviv, Ukrainian authorities said.

The Ukrainian Prosecutor General Office said that an unidentified gunman opened fire and killed the 54-year-old politician on the spot. Police are searching for the suspect, who was disguised as a delivery rider and escaped on an electric bike, local media reported.

Ukrainian President Volodymyr Zelensky condemned the killing as a "horrendous murder."

"All necessary forces and means are engaged in the investigation and search for the killer," he wrote on social platform X.

Parubiy was a leading figure in Ukraine's 2004 and 2014 protest movements and briefly served as secretary of the National Security and Defense Council. Former Ukrainian President Petro Poroshenko called the assassination "a shot fired at the heart of Ukraine."