GENEVA, JULY 24 -- A Middle Eastern youth carrying a small pistol and explosives wrapped around his waist was overpowered by the crew after hijacking an Air Afrique jetliner today and killing a French passenger to enforce a demand that he be flown to Beirut.

The hijacker, who identified himself as a Lebanese Shiite Moslem named Hussein Ali Mohammed Hariri, was seized by a Congolese steward after threatening to kill more passengers unless the plane was refueled. The steward was shot and seriously wounded as he grappled with the hijacker.

Within seconds, frightened passengers at the rear of the DC10 jumbo jet jerked open side doors and slid down emergency chutes as Swiss security police stormed inside and took the youth into custody, according to accounts from passengers and Swiss officials.

Bernard Ziegler, head of the Geneva cantonal Department of Justice and Police, told reporters the hijacker had demanded release of "a person incarcerated in West Germany" in addition to fuel for a flight to the Middle East.

Ziegler declined to identify the prisoner. But a Swiss government spokesman quoted by the Associated Press, Achille Casanova, said it was Mohammed Ali Hamadei.

Hamadei, a Lebanese Shiite arrested with liquid explosives Jan. 13 at Frankfurt airport, is scheduled to go on trial in West Germany on murder and air piracy charges after the Bonn government rejected a U.S. demand for his extradition.

U.S. authorities have accused Hamadei of participating in the hijacking of a Trans World Airlines plane to Beirut in June 1985 and the killing of a U.S. Navy diver who was a passenger on the plane.

Hamadei's brother, Abbas Ali Hamadei, was arrested at Frankfurt on Jan. 26 and has been detained in connection with the kidnaping of two West German businessmen held hostage against Mohammed Ali Hamadei's release.

The Air Afrique flight, RK056, originated last night in Brazzaville, the Congolese capital and passed through Bangui in the Central African Republic before landing in Rome this morning as a final stop before Paris, its destination.

Ziegler said the hijacker apparently boarded in Brazzaville and, after commandeering the aircraft over Milan, ordered the pilot to land at Geneva's Cointrin International Airport at 8:10 a.m. for refueling.

Aboard the plane as it landed in Geneva were 164 people, including 15 crew members, 64 French passengers, two Americans, two Britons, two Belgians, a Canadian and other passengers of various African and Latin American nationalities, Ziegler said.

The first reports of the hijacking raised fears that it might be an attempt to take the French passengers hostage as part of France's confrontation with Iran over an Iranian official wanted for questioning about last fall's terrorist bombings in Paris.

Against that background, Ziegler said Swiss authorities, with agreement from France and the Ivory Coast, where Air Afrique has its headquarters, swiftly decided the plane would not be allowed to leave Geneva. Geneva security police were preparing to attack the plane when the steward overwhelmed the hijacker and passengers began fleeing shortly before 11 a.m., he said. Twenty-nine passengers were reported injured as they slid down emergency chutes, with most suffering broken bones or bruises. Three remained in the hospital tonight, Ziegler said.

The steward, a Congolese whose identity was not disclosed pending notification of his family, was shot in the stomach as he struggled with the hijacker, Ziegler told a news conference. He was operated on for three hours at a Geneva hospital this afternoon and doctors said tonight his condition was serious.

Michel Gregoire, a French passenger at the rear of the plane, said he and several fellow passengers decided to bolt for the doors after hearing that a Frenchman had been killed in the forward section of the aircraft and after an announcement over the intercom that the plane would fly to Beirut.

"When we heard Beirut mentioned, there was no question of our leaving," said Gregoire, a 37-year-old pastry cook. "Beginning then, we felt really threatened. Something had to be done."

Ziegler praised the steward and passengers like Gregoire who precipitated an end to the hijacking. "Probably for the first time in the history of air piracy we have seen passengers and crew members take action that brought things to an end," he said.

The slain Frenchman was identified as Xavier Beaulieu, 28, a businessman residing at Pointe Noire in the Congo. He was shot in the mouth with the hijacker's Italian-made 7.65-mm. pistol, according to Commander Roland Troyon of the airport security service.

Beaulieu apparently was selected at random as the hijacker became increasingly nervous over delays in refueling the plane, according to Troyon. Although the craft was being refueled at the time, some reports said the hijacker was furious because he believed the fuel was being pumped slowly to stall for time.

After the killing, the hijacker sent crew members through the aircraft to collect passports. This created fears among French passengers they would be singled out for killing because of the French quarrel with Iran, Gregoire said.

Walter Cholewa of Toronto, who also was in the rear section, said flight attendants refused to tell him what was happening in the forward section, saying only it was "an incident." Neither he nor Gregoire heard the shot that authorities said killed Beaulieu, but fears increased when passengers with French names were summoned over the intercom to go to the first-class section, where the hijacker was.

"It is in Beirut that my problem will be resolved," Troyon quoted him as saying.

Troyon also quoted the hijacker as saying he took orders from a Lebanese town called "Burj." Burj, which is Arabic for "tower," is a prefix name used for several villages in south Lebanon as well as slum neighborhoods dominated by Shiites south of Beirut.

The hijacker gave Swiss authorities a card issued by the International Committee of the Red Cross identifying him as Hariri and saying he had been held in an Israeli prison camp.

The hijacker, born in 1966 according to the card, was being held at police headquarters in Geneva. Officials said he faces possible charges of murder and hostage taking.