MANTES-LA-JOLIE (France) • Some 2,500 people have marched in silence in honour of a policeman and his partner who were knifed to death by an extremist pledging allegiance to the Islamic State in Iraq and Syria (ISIS) group.

Many in the crowd of police, gendarmes, firefighters and locals wept as they walked on Thursday from the police station where the couple worked in the Paris suburb of Mantes-la-Jolie to their home in Magnanville where they were killed on Monday.

The attack came in the midst of the Euro football championships - already dogged by terrorism fears.

"I don't feel a form of fear, rather disappointment," said Alain, the head of a Paris police unit, who has told his officers to "be careful - we have to change our behaviour".

In Monday's assault, 25-year-old Larossi Abballa, who had served time for links to jihadist networks, killed 42-year-old police commander Jean-Baptiste Salvaing outside his home.

He then entered the house, taking Mr Salvaing's 36-year-old partner Jessica Schneider and the couple's three-year-old son hostage before slitting her throat. Ms Schneider was an employee of the police station where her partner worked. Abballa was later killed in a police raid on the house, where officers found the little boy traumatised but unhurt.

Paris prosecutor Francois Molins said police had found a hit list at the scene of the attack naming police, rappers and journalists.

Abballa, from Mantes-la-Jolie, told police negotiators before his death that he had sworn loyalty to ISIS three weeks earlier. Three associates of Abballa have been arrested and their detention was extended on Thursday for another 48 hours.

AGENCE FRANCE-PRESSE