Police on Wednesday arrested the father of two Pakistani sisters living in Spain who were lured back to their homeland last year and killed by family members in a suspected honour killing.

The man, whose identity was not given, was arrested in Terrassa, a town some 30 kilometres northwest of Barcelona where he had been living with his family for years, a police source said.

Investigators are looking to establish his connection to the alleged plot leading to the murder of his daughters, 24-year-old Aneesa Abbas and her 21-year-old sister Arooj, who had wanted to break off their forced marriages, the source said.

The pair were strangled and shot in Gujrat, a city in eastern Pakistan, on May 20, 2022, with police saying initial investigations suggested it was an "honour killing".

Six members of the girls' family were arrested shortly after the bloodshed, with one of their brothers and an uncle the main two suspects.

The Gujrat police said the two sisters had been seeking to separate from their husbands -- also their cousins -- who were still living in Pakistan and were putting pressure on the women to help them emigrate to Spain.

The family had "created a story to convince them to come to Pakistan for a couple of days", they added.

According to El Pais newspaper, the family had told them their mother, who had travelled there several months earlier, had been taken ill.

The mother, who heard the deadly attack from an adjacent room where she was being held, was rescued by police and returned to Spain where she accused one of her sons of being behind the murder, the paper said.

A brutal patriarchal practice, so-called "honour killings" involve women being put to death for bringing "shame" on their families.

In deeply-conservative Pakistan, there were more than 470 honour killings in 2021, according to figures from the Human Rights Commission of Pakistan.