A Ukrainian activist and anti-corruption campaigner has died from injuries she sustained after an acid attack three months ago, officials have reported.

Kateryna Handzyuk, 33, died in a hospital where she was being treated, Ukrainian President Petro Poroshenko confirmed Sunday evening, and called for police to conduct a full investigation.

Handzyuk was known for her open criticism of police corruption in her home town, the Black Sea port city Kherson. She was doused in sulphuric acid outside her home on July 31 and sustained life-threatening injuries.

Activists at non-governmental organizations in Ukraine have long been complaining about an increasing number of threats and attacks that they claim are not being fully investigated by law-enforcement.

"Why do we encourage people to be active in civil society, if we don't protect them when they are?" Handzyuk herself asked in a video message only a few weeks before she died.

"Attacks against civil society activists are unacceptable. The perpetrators of this vicious crime must be brought to justice," EU commissioner Johannes Hahn posted on Twitter.

Ukrainian police have arrested five men in relation to the attack.