Winnipeg police are alerting the public that a convicted sex offender who is considered a high risk to reoffend against young girls is being released from prison on Friday.

William Rupert Astle, 81, has finished a sentence for indecent exposure and breach of probation after police say he followed a nine-year-old girl around the toy section of a Winnipeg Walmart, exposed himself to her and began fondling himself. The incident took place on Feb. 1, 2014 and he was given a four-year sentence, which included a pre-sentencing credit.

Police expect him to live in Winnipeg and say he'll be under statutory release conditions until Jan. 30, 2018. Those conditions include that he not be in, near, or around places where children under the age of 18 are likely to congregate.

He'll also be under two lifetime orders prohibiting him from going to public parks or swimming areas where kids under 16 can be expected to be present, or at daycare centres, school grounds, playgrounds or community centres.

Astle's criminal record includes multiple convictions for indecent exposure related to children. He has also been convicted for sexual interference over a 10-year period, between 1990 and 2000, involving a girl who was known to him.

He was convicted in 2006 for that offence, in addition to three others in which he masturbated in public in the presence of adolescent girls, and served a sentence of one year and nine months before being released.

In 2009, he was convicted again for indecent exposure after exposing himself while watching two young girls playing in a backyard.

Vigilante activity 'will not be tolerated': police

Police describe Astle as around five-feet-seven-inches tall, with grey hair and blue eyes.

"This information is provided to enable members of the public to take suitable measures to protect themselves," police said in a release. "Any form of vigilante activity or other unreasonable conduct directed at William Astle will not be tolerated."

If you have information about Mr. Astle, police ask that you contact them at (204) 986-6222, your local RCMP detachment, or Manitoba Crime Stoppers at (204) 786-8477 or toll-free at 1-800-222-8477.