The jihadist killing of two police officials outside Paris is the latest targeted attack by an individual responding to Islamic State group propaganda, terrorism experts say.
In a video of Monday's attack reportedly live-streamed on Facebook, 25-year-old Larossi Abballa referenced Abu Mohammed al-Adnani, an IS spokesman dubbed the group's "attacks minister" by Western intelligence.
In an audio message released on May 21, Adnani called for attacks on Europe and the United States during the Muslim holy month of Ramadan, which began on June 6.
He also made a similar appeal at the same time last year, urging supporters to seek "martyrdom".
"Today we are seeing the return of targeted attacks... by individuals who have pledged allegiance to IS and act as outside agents," said terrorism expert Mathieu Guidere.
While the jihadist rampage that killed 130 ordinary Parisians in November was "indiscriminate", Abballa deliberately targeted police.
And a weekend bloodbath which killed 49 at a Florida nightclub -- also carried out by an IS-inspired attacker -- targeted the gay community, Guidere told France Inter radio.
- 'Kill police, journalists, rappers' -
The fact that IS claimed responsibility for the attack so soon afterwards reflects a well-honed strategy of "asking the individual to provide proof that he has carried out the act," said Guidere, a professor at the University of Paris.
"We are facing individuals who are serving as active external forces," he said.
In his Facebook video, Abballa urged Muslims to kill "police, journalists, public figures, prison guards and rappers," listing around a dozen well-known figures by name, according to David Thomson, a terrorism expert for French radio RFI who watched the video before it was taken down.
Paris prosecutor Francois Molins confirmed Abballa had a "hit list" of names of VIPs, police and rappers.
In September 2014, Adnani released an audio track now accessible on thousands of jihadist websites in which he urged supporters to attack "the tyrants' soldiers, their police and security forces, their intelligence (forces) and collaborators."
- 'Their blood is permitted' -
"If you are able to kill an American or European infidel -- particularly any of the hostile, impure Frenchmen... kill him by any way or means."
Al-Adnani has become a key IS figure, seen as both a motivator and supervisor of terror attacks in the West.
A Syrian from the northern Idlib region, he is a veteran of anti-American jihad in Iraq going back to the US-led invasion in 2003.
Adnani urged jihadists to use whatever weapon comes to hand -- in Abballa's case, a knife.
"If you cannot (detonate) a bomb or (fire) a bullet, arrange to meet alone with a French or an American infidel and bash his skull in with a rock, slaughter him with a knife, run him over with your car, throw him off a cliff, strangle him, or inject him with poison," he says.
Al-Adnani says there is no need to "consult anyone" as all unbelievers are fair game: "It is immaterial if the infidel is a combatant or a civilian... They are both enemies. The blood of both is permitted."
French soldiers have been repeatedly targeted by jihadists largely acting on their own since March 2012 when Islamist gunman Mohamed Merah killed three soldiers and three Jewish children and their teacher in the southwestern city of Toulouse.
In December 2014, a young man armed with a knife attacked three police officers in the central town of Joue-les-Tours while shouting "Allahu Akbar" -- Arabic for "God is greatest".
The following month, three police officers were among the 17 people killed during a wave of attacks in and around Paris that included the Charlie Hebdo massacre.
A year later, on the anniversary of the Charlie Hebdo attack, a young Tunisian armed with a butcher's knife and wearing a fake suicide vest tried to attack a Paris police station but was gunned down.