Isis has released a video of the two French attackers who brutally murdered an elderly Catholic priest in Normandy allegedly pledging allegiance to the terror group.

Both men speak in Arabic and refer to Isis’ leader Abu Bakr al-Baghdadi in the film released by the group’s Amaq propaganda agency on Wednesday.

One of the attackers holds a sign with the Isis flag printed on it.

The two men, calling themselves noms de guerre Abu Omar and Abu Jalil al-Hanfai, hold hands while sitting on the floor and swear "obedience" to Baghdadi.

Father Jacques Hamel, 86, who had served the local area for decades, had his throat slit after a pair of attackers stormed a Normandy church during a morning mass at around 10am local time on Tuesday, taking the priest, two nuns and several members of the congregation hostage.

A nun who was in the church – identified as Sister Danielle – said the priest was forced to the ground before his throat was slit.

One of the attackers has been identified as 19-year-old Adel Kermiche by French police who grew up locally and tried to travel to Syria twice last year using family members' identity documents.

Wearing a camo jacket and speaking in broken Arabic, Kermiche recites in the footage: "We pledge allegiance and obedience to Emir of the faithful Abu Bakr al-Baghdadi in hardship and in ease."

The prosecutor's office said on Wednesday the second attacker has not been formally identified. However, police have detained a 16-year-old who is understood to be the younger brother of a man who traveled to the Syria and was carrying Kermiche's ID. He was still being questioned.

Isis issued a claim of responsibility for the attack minutes after the French President François Hollande said the militant group had declared war on his country and that the government would fight the group “with all means possible”.

Normandy church attack in pictures Show all 16 1 /16 Normandy church attack in pictures Normandy church attack in pictures The victim was the 84-year-old priest at the church, Jacques Hamel. AFP/Getty Normandy church attack in pictures French police at the scene of the attack on a church in Saint-Etienne-du-Rouvray, northern France, on July 26 AFP/Getty Images Normandy church attack in pictures More police at the scene BFM TV Normandy church attack in pictures French President Francois Hollande shaking hands with security personnel at the scene AP Normandy church attack in pictures French soldiers standing guard outside the scene of the attack AP Normandy church attack in pictures A policeman secures a position in front of the city hall after two assailants had taken five people hostage in the church at Saint-Etienne-du -Rouvray near Rouen in Normandy Pascal Rossignol/Reuters Normandy church attack in pictures A policeman holds a HKG36 assault rifle as he secures the position in front of the local town hall following the attack REUTERS Normandy church attack in pictures French judicial inverstigating police apprehends a man during a raid after a hostage-taking in the church in Saint-Etienne-du-Rouvray near Rouen in Normandy, France REUTERS Normandy church attack in pictures A French policeman arrests a man following a search in a house on July 26, 2016 in the Normandy city of Saint-Etienne-du-Rouvray, where a priest was killed earlier today in the latest of a string of attacks against Western targets claimed by or blamed on the Islamic State jihadist group. French President Francois Hollande said that two men who attacked a church and slit the throat of a priest had "claimed to be from Daesh", using the Arabic name for the Islamic State group. Police said they killed two hostage-takers in the attack in the Normandy town of Saint-Etienne-du-Rouvray, 125 kilometres (77 miles) north of Paris. / AFP PHOTO / CHARLY TRIBALLEAUCHARLY TRIBALLEAU/AFP/Getty Images AFP/Getty Images Normandy church attack in pictures An undated photo shows French priest, Father Jacques Hamel of the parish of Saint-Etienne. Hamel was killed, and another person was seriously wounded after two assailants took five people hostage in the church at Saint-Etienne-du-Rouvray near Rouen in Normandy, France, July 26, 2016 in an attack on a church that was carried out by assailants linked to Islamic State. Photo Courtesy of Parish of Saint-Etienne via Reuters NO SALES. NO ARCHIVES. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED BY REUTERS AS A SERVICE TO CLIENTS. REUTERS Normandy church attack in pictures The bell tower of the church is seen after a hostage-taking in Saint-Etienne-du-Rouvray near Rouen in Normandy, France, July 26, 2016. A priest was killed with a knife and another hostage seriously wounded in an attack on a church that was carried out by assailants linked to Islamic State. REUTERS/Pascal Rossignol REUTERS Normandy church attack in pictures French policemen stand outside a house during a search in a house on July 26, 2016 in the Normandy village of Saint-Etienne du Rouvray after a priest was killed in the latest of a string of attacks against Western targets claimed by or blamed on the Islamic State jihadist group. French President said that two men who attacked a church and slit the throat of a priest had "claimed to be from Daesh", using the Arabic name for the Islamic State group. Police said they killed two hostage-takers in the attack in the Normandy town of Saint-Etienne-du-Rouvray, 125 kilometres (77 miles) north of Paris. / AFP PHOTO / MATTHIEU ALEXANDREMATTHIEU ALEXANDRE/AFP/Getty Images AFP/Getty Images Normandy church attack in pictures Police officers stand in front of a building during a search operation in Saint-Etienne-du-Rouvray, Normandy, France, following an attack on a church that left a priest dead, Tuesday, July 26, 2016. Two attackers invaded a church Tuesday during morning Mass near the Normandy city of Rouen, killing an 84-year-old priest by slitting his throat and taking hostages before being shot and killed by police, French officials said. (AP Photo/Francois Mori) AP Normandy church attack in pictures Police officers conduct a search in Saint-Etienne-du-Rouvray, Normandy, France, following an attack on a church that left a priest dead, Tuesday, July 26, 2016. Two attackers invaded a church Tuesday during morning Mass near the Normandy city of Rouen, killing an 84-year-old priest by slitting his throat and taking hostages before being shot and killed by police, French officials said. (AP Photo/Francois Mori) AP Normandy church attack in pictures French Interior Minister Bernard Cazeneuve visits the church REUTERS Normandy church attack in pictures A French policeman stands near an armoured vehicle of the French Research and Intervention Brigade (BRI) police during a search in a house on July 26, 2016 in the Normandy village of Saint-Etienne du Rouvray after a priest was killed in the latest of a string of attacks against Western targets claimed by or blamed on the Islamic State jihadist group. French President said that two men who attacked a church and slit the throat of a priest had "claimed to be from Daesh", using the Arabic name for the Islamic State group. Police said they killed two hostage-takers in the attack in the Normandy town of Saint-Etienne-du-Rouvray, 125 kilometres (77 miles) north of Paris. / AFP PHOTO / MATTHIEU ALEXANDREMATTHIEU ALEXANDRE/AFP/Getty Images AFP/Getty Images

It called the two attackers “soldiers of the Islamic State”, echoing statements on the recent attacks in Nice, Ansbach and Wurzburg.

The killing is the latest in a wave of attacks in Europe in recent weeks. There have been at least three Islamist terror incidents in Germany in the past week and the events in Nice on 14 July where a lorry driver ploughed a car into the Bastille Day crowd killing 84 people.

With the attack threat for France ranked extremely high, Interior Minister Bernard Cazeneuve said France is working to protect 56 remaining summer events and may consider cancelling some.

Defense Minister Jean-Yves Le Drian said 4,000 members of the Sentinel military force will patrol Paris, while 6,000 will patrol in the provinces. They are being bolstered by tens of thousands of police and reservists.

Mr Hollande, presided over a defence council and Cabinet meeting in Paris on Wednesday after speaking with Roman Catholic, Orthodox, Muslim and Jewish leaders.

The leader of Paris' main mosque, Dalil Boubakeur, said France's Muslims must push for better training of Muslim clerics and urged that reforming French Muslim institutions be put on the agenda.

Pope Francis, visiting Krakow, Poland, said after the attacks: "It's war, we don't have to be afraid to say this."