FILE PHOTO: French Police

French Police have arrested six people over the killing of a Policeman and his partner at their home in 2016 by an Islamist extremist, a judicial source said on Monday.

Investigators want to establish what, if any, role the six might have played in the killings in Magnanville, west of Paris in June 2016, the source said.

A 25-year-old man stabbed the couple to death and, apparently just afterwards, pledged allegiance to Islamic State in a video that the extremist group later posted online.

The attacker was killed by police who raided the house. The couple’s 3-year-old son survived.

More than 230 people were killed in terrorist attacks in France in 2015 and 2016.

Most of the attacks were claimed by Islamic State.

Another seven people have been killed in 2017 and 2018.

Most recently four were killed in a rampage by a petty criminal turned jihadist in southern France in March.

Police have foiled 51 attacks since January 2015, Prime Minister Edouard Philippe said in March.