Ukrainian President Volodymyr Zelenskyy has announced the arrest of a suspect in connection with the shooting of former parliament speaker Andriy Parubiy.

Parubiy, a leading figure in the country's pro-European protest movements of 2004 and 2014, was shot dead Saturday in the western city of Lviv.

Zelenskyy said on Monday that Internal Affairs Minister Igor Klymenko and security service chief Vasyl Maliuk had informed him of the arrest.

"The necessary investigative actions are ongoing,” he posted on social media.

"I thank our law enforcement officers for their prompt and coordinated work."

In a subsequent post, after having spoken to chief prosecutor Ruslan Kravchenko, he added, "The suspect has given an initial testimony.”

"Urgent investigative actions are currently underway to establish all the circumstances of this murder."

Earlier, authorities said a gunman had fired several shots at Parubiy, killing him on the spot.

Parubiy, 54, was a member of parliament and had been parliamentary speaker from April 2016 to August 2019.

He was also secretary of Ukraine's National Security and Defence Council from February to August 2014, a period when fighting began in eastern Ukraine.

Officials have given no immediate indication whether the murder had any direct link to Russia's war in Ukraine.