The Air France hijacking drama was the most spectacular of a string of successes for a crack French commando squad that has freed more than 500 hostages in its 20-year existence.

The slick 20-minute rescue operation on Monday, in which four terrorists but no passengers were killed, reinforced the prestige of the Intervention Group of the National Gendarmerie, one of France's most accomplished elite armed units.Known by its French acronym GIGN, the unit is comprised of just 87 men - the cream of the French police force. They are permanently on standby for emergencies such as the weekend seizure of the jetliner by Islamic extremists in Algiers.

As soon as news of the hijacking broke on Saturday, GIGN troops boarded an Air France Airbus - deliberately the same model as the commandeered jet - and headed to the Spanish island of Majorca to be at hand if Algerian authorities requested help.

About 40 assault experts, clad in black and armed with sophisticated weaponry, were involved in the late afternoon storming of the plane as it stood on the tarmac at Marseille airport, where it had flown early Monday.

When the hijackers fired on the control tower, breaking a window, the commandos - who had already been given the green light for an assault - moved into action.

With the four hijackers all in the cockpit, the commandos burst in through a front door, lobbing concussion grenades and opening fire.

Inflatable emergency slides were deployed on both sides of the plane, and passengers slid to the ground as other commandos rushed in from behind the plane.

The commandos and the hijackers, holed up in the cockpit, exchanged fire for four minutes. Three passengers were slightly injured.

Nine commandos were also wounded, including one who lost his hand throwing a grenade.

Established in 1974, the commando team is one of Europe's oldest special units and is in heavy demand to train foreign forces.

In February 1976, the team freed 30 children taken hostage on the border between Somalia and Djibouti in the Horn of Africa. Five terrorists and a girl were killed.

In December 1979, the force's commander was called to advise Saudi Arabian troops trying to quell bloody riots in the grand mosque at Mecca.

Ten years ago, the unit was called into action at Marseille airport when a hijacker seized a cargo plane with six people on board.