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Police sources say the men were discovered with their throats slit outside a building in the French capital’s 11th district. Both men died at the scene as paramedics tried to save them. The attack happened on Rue de Montreuil in the east of the French capital near Place de la Nation.

AFP GETTY/ TWITTER A father and son have died after being found with their throats slit in Paris

I saw a body in the hall, a body in the yard and a third person sitting with the firemen and policemen around. There was blood everywhere Resident

One resident told Le Parisien: "I went down. I saw a body in the hall, a body in the yard and a third person sitting with the firemen and policemen around. There was blood everywhere.” Armed police surrounded the scene as officers launched an investigation into the attack. Police have arrested a man in connection with the attack. He is said to be a family member.

LIVE images from the scene: Paris knife attack Fri, March 17, 2017 A man has been arrested suspected of slitting his father and brother's throats in the 11th district of Paris Play slideshow AFP/Getty Images 1 of 7 French members of the Research and Intervention Brigade (BRI) police unit stand guard

AFP GETTY Armed police stand guard outside a building in the 11th district

AFP GETTY The attack happened on Rue de Montreuil in the east of the French capital

Police sources have called for caution on the motives of the knifeman. Judicial police are leading the investigation. Local media say the father was killed in the courtyard of the building. The knifeman, said to be his son, is thought to have stabbed him in the stomach before slitting his throat.

TWITTER One resident said "there was blood everywhere" as police cordon off the building