Industrial leader Hanns-Martin Schleyer was found dead in a car trunk in France tonight, his throat slashed by West German terrorists who kidnaped him 45 days ago in a vain attempt to blackmail the Bonn government into freeing 11 jailed comrades.

The slaying is the latest in a wave of terrorist attacks, police counter-attacks and mysterious prison suicides this past week that has bewildered West Germany and stirred emotions around the world.

Schleyer's kidnapers made clear in a message sent to news organizations that his death was in revenge for the attack by West German commandos on a hijacked Lufthansa jet Monday and for the deaths in prison yesterday of the three leading terrorists they were trying to free.

Radical lawyers claimed yesterday that the three terrorists who died in prison may have been murdered. The West German government, however, insisted the deaths were suicides.

Officials conceded that two of the terrorists had died from bullet holes in the back of the head, but they argued that the gang leaders deliberately staged their deaths to embarrass the government.

Interior Minister Werner Maihofer charged: "Some people will push their treachery so far as to make their own suicide look like an execution."

Leftist extremists reacted to the prison deaths today by going on a rampage across Europe, protesting the "assassination of our German comrades." Radicals firebombed West German businesses and tour buses in France and Italy, and in Rome, youthful rioters stormed down the elegant Via Veneto shooting out office windows.

Hundreds of demonstrators in Genoa managed to smash in a door of the West German consulate before police dispersed the mob by firing into the air.

It was widely feared here that the fate of Schleyer was sealed the moment the commandos stormed aboard the Lufthansa jetlines in Mogadishz, Somalia, and killed three of the four hijackers who, working in consort with their Schleyer's kidnappers, had also been demanding the release of the imprisoned terrorists.

The message from the German "Red Army Faction" tonight said Schleyer's "miserabe and corrupt existence" was ended after 43 days in captivity. That would place his death on the day of the commando raid.

Although the successful rescue of the 86 Lufthansa hostages and the death in prison of the three Baader-Meinhof leaders dealt a severe blow to anarchist groups, the grim terrorist message announcing Schleyer's death tonight said:

"We will never forget the blood shed by (West German Chancellor Helmut) Schmidt and the imperialists who support him. The fight has only just begun."

Police discovered Schleyer's body when they acted on a Red Army Faction communique received by an extreme leftist Paris newspaper. The communique said the industrialist's corpse could be found in the trunk of a green Audi sedan in Mulhouse, a French town located near both the West German and Swiss borders.

Finding no body in the car, the police called in explosive experts fearing that a booby-trap might have been rigged to the trunk. They finally broke into the trunk through the back seat, and found the murdered Schleyer - his throat cut.

Earlier in the day, controversy had cotinued to mount over the prison deaths of Baader, Gudrun Ensslin and Jan-Carl Raspe.

Radial Lawyers who had defended the gang in court held a sometimes stormy press conference in Bonn suggesting that the three might have been murdered rather than committing suicide, as officials claim.

"It is not quite clear it was suicide," said one time Baader-Meinhof lawyer Otto Schily in an interview here.

"There are very large doubts because they used pistols and I can't imagine how pistols were gotten to prisoners that the West German government calls the most dangerous in the world in a maximum-security prison supervised in an incredible way every day."

Interior Minister Maihofer, however, flatly rejected such allegations, claiming he had read the preliminary report on the autopsy performed at a hospital last night and observed by specialists from three other countries. "It is absolutely impossible that anyone else was involved" Maihofer declared.

Schily, who was at the autopsy, said the bullet that killed Baader entered his neck at the back and came out through the top of his head, a somewhat contorted firing position.

Top Bonn officials said privately, however, that Baader had fired two shots into his cell wall before killing himself - to increase the suspicion that he had been murdered.

Late in the day, the Stuttgart police headquarters also announced that Baader had cordite burns on his right hand and around the bullet hole in his head - both signs of a self-inflicted wound.

Still, the fact that two handguns used by Baader and Raspe were somehow brought undetected into the maximum security cells in the most secure prison in West Germany is causing acute embarrassement and trouble for the government.

Today, the director of the prison at Stammheim near Stuttgart was fired.

The dismissal of the prison director followed the disclosure by the state prosecutor that a small and secret acvity was found in Raspe's cell - "apparently where his gun was hidden and that a small transsistor radio was also discovered conealed there todays.

The radio - which was not permitted under emergency rules - would explain how the three jailed terrorists got news of the thwarted hijacking, which then presumably led to their suicide pact.

Still unexplained, in addition to this question of how two of the terrorists got the guns, is how the three prisoners communicated with each other from solitary confinement they theoretically were barred from having any contact with each other or the outside world.

The third prisoner, Gudrun Ensslin, hanged herself from the window frame using the electrical cable from a phonograph.

When Badder's co-leader. Ulrike Meinhof, was found dead by hanging in her cell last May, similar charges of murder were lodged. Independent specialists, however, confirmed the government's ruling of suicide.

Schleyer, 62, was the head of both West Germany's employer and industrial federation, and a fervent believer in a capitalist, free market society. He was a powerful figure among the business elite, a close adviser to Chancellor Schmidt, and the embodiment of the "big business" that has made post-war West Germany prosper.

In this role, however, he was the perfect target for extremists who branded him "the fat magnate" of an economic system they wanted to destroy.

In recent months, the Red Army Faction has turned from killing law enforcement officials such as Federal Prosecutor Siegfried Buback, and has switched to kidnap-murders of powerful business figures such as bank president Juergen Ponto, killed in August, and now Schleyer.

After Ponto was killed, executives greatly increased security measures. Yet, the new breed of West German terrorists is extremely efficient and deadly. Schleyer was traveling in a two-car motorcade when he was ambushed on a Cologne street. His driver and three police bodyguards were killed.

The heavy-jowled lawyer turned industrialist was also a Nazi Party member prior to World War II and served in the SS during the war, winding up in a French prison camp for three years. His captors may have hoped this background would diminish the general public's sympathy for him as a victim.

Schleyer's family tried vainly to pay off a $15 million ransom to help free him, but his son claimed today that the government had intentionally leaked word of the plan to a news agency so the terrorists would cancel the deal.

In any event, throughout the extraordinary six weeks that Schleyer was held, Bonn never gave any indication that it would release the 11 jailed terrorists that were also part of the kidnapers' demands.

Despite the radical demonstrations today, most governments and newspapers continued to praise Bonn's tough stand against terrorism.

The Soviet news agency Tass said the "whole world sighed with relief" at the successful thwarting of the hijackers, and added: "There is no doubt that connivance with air pirates, leniency to the crimes committed by them, only encourages criminals."

The Bonn government, which earlier had expressed appreciation for U.S. and British assistance in freeing the Lufthansa hostages, also cabled thanks to the Soviet Union. France and Saudi Arabia. Schmidt told French President Valery Giscard d'Estaing that his "counsel and encouragement" had helped him withstand the ordeal.

Analysts appeared somewhat puzzled over the Soviet role in the affair, but speculated that Moscow might have intervened diplomatically when the jetliner landed in South Yemen, one of the countries the hijackers had hoped would provide a safe haven. The Yemenis flatly refused to deal with the terrorists, who then flew on to Somalia.