A memorial Mass is being celebrated in the southern French town of Trèbes, in honor of four victims killed by an Islamist gunman on Friday.

Police officer Lt-Col Arnaud Beltrame, who died saving the lives of hostages in a supermarket siege, will also be honored in a separate national memorial in Paris in coming days.

He has been hailed as a hero after trading places with a captive.

It was the worst jihadist attack under Emmanuel Macron's presidency.

The gunman, 25-year-old Redouane Lakdim, had been on an extremist watchlist and was known to authorities as a petty criminal, but intelligence services had determined he did not post a threat. He was shot dead by police.

Lakdim, who pledged allegiance to Islamic State militants, was said to have demanded the release of Salah Abdeslam, the most important surviving suspect in the 13 November 2015 attacks in Paris, which killed 130 people.

The bishop of Carcassonne and Narbonne is celebrating the Mass in the Church of Saint-Etienne in Trèbes.

The attack has shaken the rural town of 5,000 people, and flowers have been laid in front of the Super U shop where the hostage-taking took place.

Khadija, a 52-year-old restaurant owner, said she was shocked by what had occurred. "We thought this only happened in big towns," she told the AFP news agency.

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