ROME, DEC. 23 -- A runaway teen-ager flying home for Christmas hijacked a KLM jetliner with 96 other people aboard today but was captured without violence hours after he forced the plane to make an emergency landing here.

"Our experience has taught us that prudence is best," said Transport Minister Calogero Mannino amid the nearly four hours of tense negotiations at Rome's Leonardo da Vinci Airport that led to the release of the 90 passengers and six crew members, and to the hijacker's arrest.

Italian police identified the youth as Adalgiso Scioni, 15, a Sardinian who had been visiting his Dutch maternal grandparents in the Netherlands. They said he was unarmed.

In radio conversations with Italian authorities, the teen-ager claimed to have secreted a bomb in his luggage that he could trigger with a switch on his wristwatch. He repeatedly changed his demands, first asking for $1 million, then to go to Kuwait, then Chad, and ultimately asking to be taken to New York, where he wanted a hotel reservation. By then, authorities were convinced that he represented no threat.

"He is mentally unbalanced," KLM chairman Johan De Soet told reporters in Amsterdam, where the Milan-bound flight originated.

The youth, whose mother is Dutch, had run away from home in Sardinia last week after an argument with his parents, using his savings to fly to his grandparents' home in Holland, De Soet said.

The grandparents had taken him to Amsterdam airport today, and his parents were en route to the airport in Cagliari, Sardinia, to meet him when the hijacking occurred.

Humberto Improta, antiterrorist chief of the Italian police, talked the youth into releasing the passengers and crew in two stages and then led him away.

Italian authorities and officials of the Dutch flag carrier in Holland said the hijacking occurred as KLM flight 343, a Boeing 737, approached Milan.