HELSINKI—Corrections officials in Finland say a triple murderer has slipped out of a low-security prison a month ahead of his scheduled release — the sixth time he has escaped custody.

Deputy director of Kerava Prison Jukka Hannula says Nikita Fouganthine left a construction site at the low-security prison early Wednesday while serving a four-month sentence for breaking parole.

Fouganthine was convicted in Sweden of the 1988 murders of a father, mother and son, and was transferred to serve out his life sentence in Finland.

He managed to escape four times but by 2009 prison officials said he had changed his ways, commuted his sentence and he was released on parole. He has returned to jail twice since then on parole violations — and escaped twice.