French soldiers shot and a killed a man on Sunday after he stabbed to death two women at Marseille's main train station, the French interior ministry said, in what police sources called a "likely terrorist act".
Three police sources said the suspect had shouted "Allahu Akbar" as he carried out his attack. No further details were immediately available.
Police cordoned off the area and told people to stay away.
A witness told Reuters she saw a man take out a knife from his sleeve and then stab a young girl and then a second woman, shouting what could have been "Allahu Akbar". She added that she saw soldiers from France's Sentinelle force who were patrolling in the area arrive on the public square at the Gare Saint-Charles station.
"After the attack carried out next to Marseille Saint-Charles, I am immediately going to the site of the attack," French Interior Minister Gerard Collomb said on Twitter.
France has been in a state of emergency following a spate of attacks by Islamist militants over the last two years, including attacks in Paris in November 2015 which killed 130 people.
A gunman drove a heavy truck into a crowd celebrating Bastille Day in the city of Nice last year, killing 86 people and injuring scores more.