More than one thousand Ukrainians have protested in front of the constitutional court in Kyiv against a decision to invalidate certain anti-corruption measures.
Some activists threw smoke grenades into the building and threatened to invade the premises, while police did not intervene with the demonstrations.
Others held placards on Friday, reading "Corruption Court of Ukraine" and "Out with the pigs of the Constitutional Court".
On Wednesday, the country's Constitutional Court announced it had scrapped anti-corruption laws that had been in force for several years, judging them too severe.
Criminal liability will no longer be enforced for civil servants found guilty of filing false tax returns, an offence punishable until then by two years in prison.
Meanwhile, the move also reduced the powers of the government agency responsible for monitoring such returns.
The decision was made after the court had been sized by around 50 pro-Russian MPs.
The announcement caused a strong outcry across Ukraine and President Volodymyr Zelensky labelled the decision "unacceptable" and a "threat to national security".
Zelensky also demanded that new draft anti-corruption laws be prepared and that the circumstances of the ruling be investigated, following an emergency meetingof the Security Council.
Ukraine's judiciary is considered notoriously corrupt and several Constitutional Court judges are themselves under criminal investigation for false statements.
Cancellation of the reform could result in the suspension of Western financial assistance on which Ukraine is heavily dependent and the end of a visa-free regime with the European Union for Ukrainians.
"Such actions of the Court have a number of not just negative, but catastrophic consequences in both the domestic and foreign policy dimensions of our country," said Zelensky.
"[But] we must not allow the street to start settling this problem at will."