Police say four prison guards have been injured in clashes with inmates who have barricaded themselves in a prison in Ukraine's port city of Odessa.

Serhiy Shaykhet, chief of the investigative unit at the Odessa police, said in televised remarks Monday that police are negotiating with the inmates.

Earlier reports indicated that several inmates have been injured and that some prisoners have escaped. Local website Dumskaya carried pictures of people detained just outside the prison walls and taken back inside. The police official, when asked about the incident, could not immediately say who the people were.

Several activists who gathered outside the prison said the inmates are protesting against the poor quality of food.