An investigator in Russia's northern city of Saint Petersburg was sentenced to prison on Friday for freeing a jailed convict with whom she had fallen in love, prosecutors said.

The city's Kuibyshevsky district court sentenced Yana Antonova to a year and eight months in prison for abusing her position after she "for personal reasons freed a man accused of a serious crime," prosecutors said in a statement.

Antonova, a 35-year-old police investigator, fell in love with the convict, Mikhail Beryukov, as she investigated a case in which he was involved, the Komsomolskaya Pravda newspaper reported, citing a police source.

Beryukov was being investigated for fraud and also had a previous murder conviction, the ITAR-TASS state news agency reported.

In February 2009, Antonova faked a document ordering him to be transferred from a pre-trial detention center in Saint Petersburg to one in the nearby Novgorod region, prosecutors said.

She then dismissed a police convoy assigned to transfer Beryukov and took him to an apartment where they spent the night, prosecutors said. He was detained by police a few days later at the apartment.

Antonova confessed to police that she was harboring Beryukov after he spent his days of freedom taking drugs and refused to return to the detention center, ITAR-TASS reported.