A Ukrainian political activist said he suffered chemical burns on Tuesday after an assailant threw green liquid in his face during a demonstration outside a prosecutor's office in Kiev.
Most of Vitaliy Shabunin's face and his left hand were covered in bright green stains similar to marks left by a green solution, known as "zelyonka", which is sold locally as an antiseptic.
"I'm sorry my eyes are closed. I have a chemical burn," Mr Shabunin, the head of the non-governmental Anti-Corruption Action Center said in a video post.
The incident comes amid a spate of violence against anti-corruption activists and minority groups, which non-governmental organisations said highlights a culture of impunity at odds with commitments from the authorities.
Transparency International Ukraine said the attack against Mr Shabunin, which also involved assailants pelting him with cake, represented a "a negative tendency: escalation of unpunished violence against anti-corruption activists".
"This situation is a shame for the law enforcement system. We demand that the management of law enforcement agencies pay attention to these cases and report on their investigation," it said in a statement.
Since the pro-European leadership came to power in 2014, Ukraine has received billions of dollars in financial aid from Western allies in exchange for promises to eliminate corruption and conform to international democratic and human rights standards.
At Tuesday's protest, Mr Shabunin and a small group of activists were calling for the resignation of the special anti-corruption prosecutor over a decision to close an investigation into the interior minister Arsen Avakov's son.
The ministry has said the case was politically motivated, while Mr Avakov has denied his son embezzled state money.