PARIS (AFP) - French authorities said on Monday that anti-terror investigators were making progress in a probe into the stabbing of a French soldier, as he was released from hospital following the brazen knife attack.

The attack on Saturday in a busy underground shopping and transport hub echoed the grisly killing of another soldier in London, but authorities have not yet established a link between the two cases.

Interior Minister Manuel Valls told Canal+ on Monday that police had "serious leads" on the identity of the attacker, who stabbed French soldier Cedric Cordiez in the neck while he was on patrol with two colleagues.

The attacker, described by police as bearded and around 1.9m tall, approached the 23-year-old soldier, stabbed him and then disappeared into a crowd.

Sources close to the investigation said that the suspect was caught praying on video a few minutes prior to the attack and that a plastic bag containing a bottle, a knife and rubbish was found nearby.

Mr Cordiez meanwhile was released from a military hospital on Monday morning and had rejoined his unit, military officials said.

Police in France are seeking to determine if the attack was a copycat of the brutal murder of the British soldier in London last Wednesday.

The key suspect in that attack, Michael Adebolajo, was captured on video carrying bloodied knives and a meat cleaver after the attack, saying he had murdered off-duty soldier Lee Rigby because British troops were killing Muslims.