An artist's sketch of Clifford Olson at his faint-hope hearing in 1997.

Prime Minister Stephen Harper has ordered a review of Canada's old-age income support programs in light of reports serial killer Clifford Olson is receiving monthly payments.

Olson, 70, killed at least 11 boys and girls in B.C. before he was imprisoned for life in 1982. As a senior without another income, he is entitled to Old Age Security and the Guaranteed Income Supplement.

The two programs pay the killer, and several hundred other convicts behind bars, more than $1,100 a month each.

The money has been going into a trust fund for Olson, who is serving 11 life sentences in a maximum security prison.

"I must admit that I'm as upset about this, as concerned about this as any other Canadian is," Harper told reporters in London, Ont., on Thursday.

Clifford Olson, then 41, leaves provincial court in Chilliwack, B.C., on Aug. 8, 1981. (Canadian Press)

"I think probably the reason this hasn't arisen before is this is unusual. These are unusual circumstances. It is not typical that we have senior citizens facing life incarceration."

Harper has asked Diane Finley, the minister of human resources, to look at ways to change the old age pension system, "because it should be rectified," he said.

Olson, who has never shown any remorse for his horrific crimes, was paid $100,000 by the RCMP to lead them to the bodies of his victims. That money was later put in trust for his estranged wife and son.