Iraq’s prime minister has warned that ISIL militants planned attacks on the metro transport network in Paris and subway systems in the US. He reportedly said the information “looks credible.”

However a senior US official has said nobody in the US government is aware of a purported plot to attack transport systems in France and the US.

Meanwhile French fighter jets struck ISIL targets in Iraq and the US hit them in Syria as a coalition to destroy the militant group gained momentum on Thursday with an announcement that Britain would join.

French Prime Minister Manuel Valls told reporters: “France will never give in, France does not give into intimidation, that’s the reaction we owe our fellow citizen who was assassinated.”

Muslim leaders in France have condemned the death of Hervé Gourdel as an “unspeakable horror” and a “barbarity.”

They have called for Muslims to gather outside the Paris Mosque on Friday to show their united condemnation of the crime.

In the Arab quarter of Belleville in Paris there was anger against ISIL and the impact they were having on ordinary Muslims.

“Its us who will pay the price,” said one man.” All the people will pay the price here. It’s their fault and we have to pay the price.”

Throughout the weekend, flags will be at half-mast across France to pay tribute to the 55-year-old French father and mountain guide who met a gruesome end at the hands of jihadists in Algeria.