French President Francois Hollande said Tuesday that the killing of a police commander and his companion, who worked at a police station, by a man allegedly pledging allegiance to Islamic State was "incontestably a terrorist act."
The anti-terrorism unit of the Paris prosecutor's office has taken over the investigation after special police forces, who killed the suspect, said he invoked the Islamic State extremist group during negotiations, a judicial source told dpa.
"The author of this attack himself wanted it to be recognized as terrorist," Hollande said.
The president held an emergency cabinet meeting at the Elysee Palace following the attack, which took place overnight in Magnanville, approximately 50 kilometres west of Paris.
Interior Minister Bernard Cazeneuve said after the meeting that the threat of terrorism was "elevated in France, elevated in Europe and elevated in the West, as we have seen with the events that took place 48 hours ago in the US."
On Sunday, the lone gunman who killed 49 people in a gay nightclub in Orlando, Florida, pledged allegiance to Islamic State in an emergency call while the attack was under way.
Cazeneuve said that since the beginning of the year, more than 100 people had been arrested who represented a threat to France's security.
The police commander was killed at knifepoint. His female companion, who was a secretary for a police station, was also found dead inside their home. Ministry spokesman Pierre-Henry Brandet said the attacker was killed by police special forces.
The couple's 3-year-old son was found unharmed inside the home, the Elysee said.
According to the SITE monitoring group, which tracks extremist activity online, Islamic State said on its Amaq news service that the attacker was one of its soldiers. Amaq is one of the extremist group's many media outlets.
France has seen a string of terrorist attacks and attempted terrorist attacks since the beginning of 2015, when journalists at a satirical magazine were shot by two brothers claiming allegiance to Islamic State.
In November, 130 people died in coordinated attacks around Paris that Islamic State also claimed responsibility for.