Hundreds of Muslims gathered outside Paris' main mosque on Friday to denounce the beheading of French tourist Herve Gourdel by militants in Algeria who said their act was a response to France's air strikes against Islamic State fighters.France's five-million-strong Muslim population is the largest in Europe. Some on the French right have suggested the community has not condemned Gourdel's murder this week strongly enough, a charge its leaders reject."He was the victim of a cowardly murder," Dalil Boubakeur, rector of the Grand Mosque of Paris, told hundreds of Muslims gathered outside the mosque after noon prayers."Islam demands respect for life ... The Koran tells us that to kill one man is to kill all humanity," he said.In a video released by his captors on Wednesday, 55-year-old tour guide Gourdel is seen kneeling with his arms tied behind his back before four masked militants. The video does not show the beheading but a militant holds the head up to the camera.France was the first Western country to join the US-led air strikes on targets in Iraq. Its jets have carried out a new attack since the killing of Gourdel and a poll on Friday showed public support for intervention had surged to nearly 69 percent.The crowd that gathered after Friday prayers in Paris was made up largely of French people of north African origin, many of them middle-aged or elderly. Several dozen Muslims also gathered in the western city of Nantes."This is not Islam, what they are doing," said Mohamed Benbouzia, an elderly man of Algerian origin who said he had worked for 30 years at a Renault car factory."It is a perversion, by sick people, murderers, criminals, people who should be sitting in jail," he said. "The Algerian government must do absolutely everything it can to track down the people who did this and bring them to justice."Zohra Lamloum, a French teacher of Algerian origin at a high school in a Paris suburb, said she was 10 years older than Gourdel and felt like he was her "younger brother."Holding up a newspaper and pointing at a photograph of Gourdel, she said: "He was a healthy man, somebody who went hiking, who lived cleanly, who went to our country with the purest intentions, and this is what happened to him."The people who did this are drug addicts, imbeciles, they have no heart."Iraqi Prime Minister Haider al-Abadi said on Thursday his country had received "credible" intelligence that Islamic State militants planned to attack subway systems in Paris and in the United States.US and French officials said then that they had no evidence to back up the prime minister's warning.French Foreign Minister Laurent Fabius said on Friday there had been no confirmation of the Iraqi information about possible attacks on the Paris subway system by Islamic State militants.