Muslim community leaders in northern France have refused to prepare the funeral for a Daesh terrorist in accordance with the Islamic tradition, reports said on Saturday, while a vigil is expected to be held for the priest in a bid to forge unity between communities in the country.

19 year-old Adel Kermiche, who recently killed priest Jacques Hamel during mass in Saint-Etienne-du-Rouvray church will not be buried in line with Islamic principles, an imam reportedly told French Daily Le Parisien.

"We won't dishonor Islam with this person" the president of a local Muslim cultural association Mohammad Karabila said and added that the Muslim community will not attend the preparation or burial ceremony for the terrorist.

Reports also note that Muslims support the decision, saying that Kermiche is not a part of the Muslim community.

Meanwhile, Muslim and Christian groups will hold vigils for priest Hamel and a regional Muslim council has planned a "brotherhood march" in the southeastern city of Lyon, AFP reported.

A church in Bordeaux said it would hold a non-denominational vigil for the 85-year-old Jacques Hamel, who had his throat slit by Daesh-inspired teenaged attackers.

And prayers were also planned at the Saint-Etienne church where the killing took place as Hamel was celebrating mass on Tuesday.

Meanwhile, police were still trying to piece together links to the two 19-year-olds who carried out the attack, Adel Kermiche and Abdel Malik Petitjean -- both of whom were on intelligence services' radar and had tried to go to Syria.

On Friday, authorities filed charges against a 19-year-old man accused of "criminal conspiracy with terrorists" after police discovered a mobile phone video of one of the assailants at his home.

Police were still questioning Petitjean's cousin and a Syrian refugee, after a photocopy of his passport found at Kermiche's house.

A 16-year-old was released but could ultimately face a separate investigation for possessing terrorist propaganda, authorities added.

A source close to the enquiry said that a 17-year-old, who had tried to travel to Syria with Kermiche, was arrested in Geneva and sent back to France just a few days before the attack.

However, "nothing suggests he was in any way implicated in the attack" at this stage, the source added.