A man who allegedly killed a German tourist and injured a British national in a suspected terror attack in Paris had pledged allegiance to the so-called Islamic State, authorities said.

The man, named by AP as Armand Rajabpour-Miyandoab, is accused of stabbing the German-Filipino man to death before using a hammer to injure a British man and a French national on Saturday near the Eiffel Tower.

France’s anti-terrorism prosecutor Jean-Francois Ricard said he had opened an investigation into the attack on Sunday.

He said Rajabpour-Miyandoab, a French national, had posted a video on X before the attack pledging his allegiance to IS alongside other recent posts in which he made references to the Israel-Hamas war.

Mr Ricard said Rajabpour-Miyandoab, born in 1997, converted to Islam at the age of 18 and in 2016 planned on joining IS in Syria before being imprisoned for four years on a charge of planning violence.

He received psychiatric treatment and was under surveillance for suspected extremism, the prosecutor confirmed.

Three other people from Rajabpour-Miyandoab’s entourage and family have been detained by police for questioning, Mr Ricard said.

After killing the tourist, the attacker crossed the bridge to the city’s right bank and injured the British and French nationals, authorities said.

Mr Ricard said both of them were able to get back home on Sunday.

The suspect cried “Allahu Akbar” (God is great) and a police officer twice tasered the suspect before arresting him, authorities said.

French interior minister Gerald Darmanin reportedly said that when questioned by police, the suspect expressed anguish about Muslims dying, notably in Afghanistan and the Palestinian territories, and claimed that France was an accomplice.

I send all my condolences to the family and loved ones of the German national who died this evening during the terrorist attack in Paris and think with emotion of the people currently injured and in care

Mr Darmanin said “this person was ready to kill others”, and praised the quick response of the police.

In a statement to the PA news agency, a spokesperson for the British Foreign Office said: “We are supporting a British man who was injured in Paris and are in contact with the local authorities”.

Writing on X on Saturday, France’s president Emmanuel Macron said: “I send all my condolences to the family and loved ones of the German national who died this evening during the terrorist attack in Paris and think with emotion of the people currently injured and in care.

“My most sincere thanks to the emergency forces who made it possible to quickly arrest a suspect.”