Media playback is unsupported on your device Media caption BBC's Lee Carter: "Investigators say they believe the victims were killed before they were placed in the car"

Three members of an Afghan immigrant family in Canada have been convicted of murdering four female relatives in a so-called "honour" killing.

The bodies - three teenage girls and their father's first wife - were found in a car submerged in a canal in the city of Kingston, Ontario, in 2009.

The girls' father, brother and mother will serve at least 25 years in prison.

Prosecutors said the father was angered that his two eldest daughters wanted boyfriends, in defiance of his values.

The court heard how Mohammad Shafia had become increasingly angry and upset with his three teenage daughters for having secret relationships with boys and wearing revealing clothes.

'Twisted notion of honour'

The prosecution relied heavily on wiretap recordings that revealed the level of Shafia's anger and comments in which he referred to his dead daughters as whores.

"The apparent reason behind these cold shameful murders was that four (victims) offended your twisted notion of honour," the judge, Justice Robert Maranger, told Shafia and his two co-accused, his wife Tooba Yahya and their son Hamed.

The BBC's Lee Carter, in Toronto, says the three-month trial riveted the country.

After the verdict was read out, Mohammad Shafia, speaking through a translator, said, "We are not criminals, we are not murderers, we didn't commit the murder and this is unjust.''

The bodies of sisters Zainab, Sahar and Geeti Shafia, aged 19, 17 and 13, were found along with the body of their father's first wife, Rona Amir Mohammad, in the Rideau Canal in June 2009.

They had been on a visit to Niagara Falls and were returning home to Montreal when they stopped for the night near Kingston.

The prosecution alleged Mohammed, Tooba and Hamed drowned their four victims, placed their bodies in the car and then pushed it into the canal with the family's other car.

The court heard the girls lived in an abusive home and received frequent death threats, in part over the fact that the two eldest daughters had boyfriends without their father's approval.

The jury was told the decision to murder the four women was taken after 19-year-old Zainab took refuge in a shelter, defying her male relatives.

The defence said their deaths were the result of a joyride gone wrong after Zainab took the wheel

Ms Mohammad, 52, wanted a divorce and supported the girls' wish to live according to Western norms.

The prosecution presented wiretap evidence, including one conversation where Mohammad Shafia said his daughters "betrayed us immensely."

In other recordings, he was heard calling them treacherous and whores and calling on the devil to defecate on their graves.

The 10-member Shafia family left Afghanistan in 1992. They came to Canada in 2007, having previously lived in Australia, Pakistan and Dubai.

Shafia married Tooba Yahya because his first wife was unable to have children.

She was living with Shafia and Yahya at the time of her murder. The polygamous relationship, if revealed, could have resulted in their deportation.