Websites of several Ukrainian ministries could not be reached on Friday because they were hacked.

People visiting sites of the Ministry of Education and the Ministry of Foreign Affairs, among others, may see a message stating that personal data of all Ukrainian citizens has been erased from the agencies' computers.

The messages are displayed in Ukrainian, Russian and Polish.

It also states that the personal data will be made public.

It is unknown who is behind the attacks.

It is also unclear whether the hackers actually have data in their hands and if so, which personal data is involved.

The message ends with a cryptic message.

It states that it is about "vengeance for Volynia, the Organization of Ukrainian Nationalists, the Ukrainian Resistance Army, Galicia, Polesia and the historical countries".

Volynia, Galicia and Polesia are regions in the border areas between Ukraine, Poland, Belarus and Russia.

The Organization of Ukrainian Nationalists and the resulting Ukrainian Resistance Army were far-right organizations before and during World War II.