A Tunisian man who killed three people in a church in France only recently arrived in Europe, officials say.
The suspect, 21, had an Italian Red Cross document, issued after he arrived on the Italian island of Lampedusa by migrant boat last month.
He was shot by police and is in a critical condition. One of the victims was “virtually beheaded”, said the French chief anti-terrorism prosecutor.
President Emmanuel Macron said it was an “Islamist terrorist attack”.
Mr Macron said the number of soldiers being deployed to protect public places – such as churches and schools – would rise from 3,000 to 7,000. Anti-terror prosecutors have opened an investigation, and France has raised its national security alert to the highest level.
In another development, a 47-year-old man believed to have been in contact with the attacker was detained by police late on Thursday, French media reported.