The US airman who was stabbed while overpowering a gunman armed with a Kalashnikov on a Paris-bound train has left hospital.

Spencer Stone's arm was bandaged and in a sling as he left the hospital in Lille, northern France, on Saturday evening.

While in hospital he had surgery on his hand, which is understood to have gone well.

The 23-year-old waved to the waiting media and was driven off in a black car with diplomatic licence plates.

Mr Stone, who is on leave from the US Air Force, and his friend Alek Skarlatos, tackled the suspected gunman, who also had an automatic pistol and a knife.

Their friend, university student Anthony Sadler, 23, helped to subdue the suspect and British grandfather Chris Norman helped them tie him up.

The suspect, a 26-year-old Moroccan national, slashed Mr Stone several times with a box-cutter knife during the altercation on Friday.

The train, which was in Belgium, was rerouted to the nearest station in Arras, northern France, where the suspect was arrested.

Mr Norman said without Mr Skarlatos and Mr Stone "we'd all be dead".

Mr Stone has also been praised for providing medical treatment to another passenger whose throat was slashed. He remains in a critical condition.

A French-American man was also shot in the chest. He was in serious but stable condition, authorities said.

Commendations

US President Barack Obama telephoned Mr Stone, Mr Skarlatos and Mr Sadler to commend and congratulate them.

Other world leaders, including British Prime Minister David Cameron and French President Francois Hollande, also praised them and Mr Norman.

The three friends, who grew up together in California and had been on a European holiday, also made their families proud.

Mr Stone's mother, Joyce Eskel, said she had talked to her son from hospital: "I'm just crying because I could've lost my son so easily.

"He's always been a hero to me. Now he's an actual hero. He deserves it. He put his life on the line. They all did."

Mr Skarlatos had only recently returned from a tour of Afghanistan.

His father, Emanuel Skarlatos, said: "A guy comes back from Afghanistan and he has to fight a battle on vacation on a train in France."

Mr Sadler's father, Tony, said: "He leaves here a young man on an excursion to broaden his world view and to have fun with his buddies, and he comes back France's national hero.

"He might even meet the president of France before he leaves, so I'm still wrapping my head around that."

Mr Norman, a married 62-year-old IT consultant who lives in France, said he helped the boys because he thought he was "probably going to die anyway".

"I would rather die being active, trying to get him down than simply sit in the corner and be shot," he told reporters after giving evidence at a police station in Arras.

He and the two uninjured Americans received bravery medals from the local mayor immediately after the attack.

Among the 554 people on board the Amsterdam-Paris train was French actor Jean-Hugues Anglade, the star of Betty Blue and Nikita.

He was hit by breaking glass as the alarm went off.

Anglade told Paris Match magazine that when the shooting started, the train staff went into a private cabin and locked it, leaving the passengers alone.

He said: "I really could see us all dying because we were all prisoners in that train, it would have been impossible to escape from that nightmare."

But he added: "We were stuck in the wrong place with the right people. It's miraculous."

Suspect

The suspect, who is believed to have recently travelled to Syria, is being questioned by French police after opening fire on the train as it passed through Belgium.

The 26-year-old Moroccan national, named by Spanish media as Ayoub el Khazzani, was moved to the anti-terror police headquarters outside Paris on Saturday morning and can be held for up to 96 hours.

French authorities say the suspect had previously lived in the southern Spanish city of Algeciras and frequented a mosque under surveillance there.

Spanish authorities had informed French intelligence about him because he belongs to a "radical Islamist movement", French interior minister Bernard Cazeneuve said.

French police confirmed through fingerprints the man had been on their radar since February 2014.

He was also known to the Belgian authorities, reports say.

It also emerged the suspect is thought to have travelled to Syria in the last few months.

An unnamed French official close to the investigation told the Associated Press that French authorities were alerted the suspect flew to Turkey from Berlin on 10 May.

Would-be jihadists often head to Syria via Turkey.

The suspect was also arrested in Spain at least once for a drug-related offence, a source in Spanish counter-terrorism told Reuters.

But the man's lawyer said his his client had been shocked and surprised "to the point of being amused" when he was arrested.

He told police he found a bag in a park in Brussels containing guns and a knife and the idea came to him to rob people.