Alexander Pichushkin, a Russian serial killer jailed for life in 2007 for killing 48 people, has said he is ready to confess to 11 more murders, Russia's penal service said on Saturday.

Pichushkin, now 50 years old, targeted his victims, often homeless people, alcoholics and the elderly, around Bitsevsky Park, a large green place in southern Moscow. His killings lasted from 1992 to 2006.

He was nicknamed “the chessboard killer” by the Russian media because he told detectives in a confession that he had hoped to put a coin on every square of a 64-square chessboard for each of his victims.

Pichushkin has been held at the Polar Owl prison, in Russia’s remote Arctic north, since being sentenced.

In a statement published on the Telegram messenger app on Saturday, Russia’s penal service said that Pichushkin had told investigators he was ready to confess to 11 more murders of men and women.

Pichushkin has long been suspected of additional murders to those for which he was convicted.

He claimed during his trial to have killed 63 people, but prosecutors only charged him with 48 murders and three attempted murders.

If convicted of the additional murders, it would make Pichushkin Russia’s second most prolific serial killer on record, behind Mikhail Popkov, a former policeman convicted of 78 murders.