BELLEVILLE, Ontario (Reuters) – A top Canadian military commander whose obsession with stealing women's underwear escalated into two horrific sex murders was jailed for life on Thursday without possibility of parole for 25 years.

Colonel Russell Williams, who was in charge of Canada's largest air force base and who once flew Queen Elizabeth's plane, had pleaded guilty to killing two women in separate attacks. Police said it was likely he would serve his sentence in solitary confinement.

In a case that appalled Canada, the court heard Williams had videotaped himself raping the women, capturing their pleas for mercy, and then filmed them as they died.

"I stand before you indescribably ashamed... I deeply regret what I have done and the harm I know I have caused to many. I committed despicable crimes," he told the judge tearfully before being sentenced.

A prosecution lawyer described the 47-year-old as "one of the worst offenders in Canadian history". The videos, which were not shown in court, will be destroyed when Williams dies.

The court heard that Williams started off by breaking into homes in eastern Ontario and stealing underwear. He sometimes took photos of himself wearing bras and panties.

Last November he entered the house of Marie-France Comeau, 38, and sexually assaulted her for hours before putting duct tape over her mouth and nose. Comeau, a corporal at the Trenton air base where Williams was commander, suffocated to death.

In January this year he abducted 27-year-old Jessica Lloyd, drove her to his house and then repeatedly raped her. He strangled her to death with a rope and later dumped the body by a rural road.

Williams was arrested in February after a police roadside check discovered the distinctive tire marks outside Lloyd's house had been made by his SUV.

"As long as he dies in jail, I'm happy," Lloyd's brother Andy told reporters outside the court.

Prime Minister Stephen Harper said "our thoughts go out to all members of the Canadian Forces ... who have been very badly wounded and betrayed by all of this."