A wave of bombings and shootings by left-wing extremists during the past two months has stirred anxiety across Europe that terrorist groups are pooling skills and resources to carry out a coordinated campaign of violence against western military and industrial targets.

European security experts are divided over whether the attacks mark the emergence of new cross-border terrorism dedicated to sabotaging allied defenses, or whether they reflect a final spasm of violence by remnants of urban guerrilla groups that carried out murders and kidnapings in the 1970s.

They also disagree over the scope of a terrorist network in Europe. West German and French investigators say evidence of active collaboration is limited to fewer than 40 hard-core activists circulating in Belgium, France and West Germany. Attacks on U.S. and NATO targets in Portugal, Spain, Greece and the Netherlands have been dismissed as "bandwagon bombings" carried out by small, unconnected teams of leftist extremists.

But others see a broader, more sinister conspiracy at work. Italian Interior Minister Oscar Luigi Scalfaro, who is touring European capitals to forge better international cooperation in combating terrorism, believes there may be "an organizational center" guiding "an international matrix" of terrorism.

"We can be sure that there is a precise plan, a brain, a political line and that a terrorist way of waging war exists," Scalfaro said.

French former foreign minister Claude Cheysson, now a member of the European Community's Executive Commission, draws a clear link between the terrorism in Europe and a grand strategy masterminded abroad.

"Terrorism is the most efficient method of destabilizing a democracy," he said. "The encouragement of terrorism by totalitarian regimes is clear, just as the encouragement by democratic countries of human rights and freedom of expression in totalitarian regimes is clear."

While noting that Moscow may benefit from turmoil fomented by urban guerrillas in Europe, French security experts said they have no direct evidence linking the Soviets to the spate of recent attacks. "We don't think that there is a chef d'orchestre in Moscow conducting all this," a French official said.

West German counterterror specialists said that apart from similar propaganda language attacking "western imperialism," they have not discerned any connections between Moscow and the Red Army Faction urban guerrilla group.

European security experts also have discounted direct involvement by Middle Eastern groups in the current wave of bombings. Belgian officials said recent warnings that Islamic Jihad, which has claimed a number of major terrorist attacks in Beirut, was planning to strike U.S. and NATO targets in Brussels have proved unrelated to actions by European terrorists.

The only firm evidence of violent collaboration that investigators are now pursuing seriously is the proclaimed alliance between the Red Army Faction, formerly known as the Baader-Meinhof gang, and France's Direct Action, and investigators suspect that the West German group carried out the recent assassination of a French Defense Ministry arms sales official.

Both groups have used the same explosives, stolen from a quarry in Belgium last year, to carry out bomb attacks in recent months.

On Jan. 15, the two groups issued a joint statement declaring they were merging forces in a united anti-NATO front. But police say they have accumulated much information indicating that French and West German extremists have been cooperating for years.

Until the late 1970s, the RAF's main international contacts were with Middle Eastern radicals, according to West German security experts. They said relations were established through training camps in southern Lebanon and South Yemen, as well as alleged infusions of weapons and cash from Libya.

But the Middle Eastern channel of cooperation was severed in 1977, West German authorities said, when an RAF hijacking conducted with the aid of Arab radicals was foiled by West German commandos.

In the years that followed, as the RAF suffered a string of defeats through the arrest of key leaders and the confiscation of funds and arms, the remaining corps of terrorists sought new havens of refuge by developing contacts among left-wing extremists in neighboring countries.

The tight security dragnet within West Germany and the ease of transit across European frontiers reinforced the desire of Red Army Faction members at large to break out of their "isolation" by stepping up their frequent crossings into France, West German security experts said.

This opening of a strong "French connection" coincided with the revival in France of the extreme left-wing group Direct Action. In May 1981, several key members, including leader Jean-Marc Rouillan, were granted amnesty by the new Socialist government.

In May 1982, a 20-page RAF "action paper" began to circulate among left-wing groups urging a new crusade that would forge a "guerrilla, resistance and anti-imperialist front" through coordinated attacks on military targets.

Meanwhile, the continuing arrests of terrorist suspects in West Germany, coupled with the successful crackdown in Italy on the Red Brigades, soon turned France into a favored place of exile for left-wing extremists.

The first signs of a newly emerging West European terror offensive occurred last October when a Belgian group, known as the Fighting Communist Cells, staged a series of bomb attacks against NATO installations including explosions aimed at a strategic fuel pipeline.

Last July, police in Frankfurt found a map of NATO's fuel pipeline system during a raid on a Red Army Faction hideout.

Belgian officials say that Direct Action is known to have maintained close ties with the Fighting Communist Cells.

The three-way link has become more apparent since December, when 30 jailed RAF terrorists began a hunger strike in West Germany to dramatize their demands to be assembled together and treated as political prisoners. More bomb attacks launched by all three groups endorsed the hunger strikers' demands. On Jan. 19, five imprisoned Direct Action members also started a fast to show solidarity with their German comrades.

West German police believed that the terrorists would only escalate their campaign of violence from attacks on property to attacks on individuals if one of the hunger strikers died.

But on Jan. 25, Rene Audran, the director of international arms sales at the French Defense Ministry, was gunned down outside his home near Paris. A week later, Ernst Zimmermann, chief executive for the MTU engineering firm that makes engines for NATO tanks and aircraft, was slain by two terrorists in Munich. His death turned out to be a signal for the jailed extremists to abandon their fasts.

Since then, two new Red Army Faction letters have confirmed that the group's goal is to create a unified West European urban guerrilla movement that will "shake the imperialist system."

Investigators sifting through the evidence of both killings say they were perpetrated in both cases by hard-core RAF activists, even though Audran's death was claimed by Direct Action.

French and West German police said Direct Action is probably playing a subordinate role and is furnishing only "logistical support" while RAF members carry out acts of terror.

Security officials said that French police reportedly spotted several known German extremists in Paris several days before Audran's assassination. A woman with a German accent also called Audran's home the night of his murder. The statement citing responsibility for his death was written in flawless German but imperfect French.

French and German investigators put the estimated strength of hard-core Red Army Faction activists at between 20 and 30, while Direct Action has as few as 10 members and the Fighting Communist Cells a half dozen still at large.

What remains uncertain, security experts say, is whether the RAF and Direct Action have managed to mobilize some of the Italian extremists now in exile in France.

Prime Minister Bettino Craxi told the Italian parliament last week that "anti-NATO themes that inspire the new terrorism were part of Italian subversion as far back as 1980 and 1981, when the Red Brigades selected the men and structures of the Atlantic Alliance as the primary objectives of their strategy."

Craxi said 117 Italian extremists are known to be living in France and another 44 are believed to be there. Italy has made 120 extradition requests, none of which has been honored by France.

Italian officials have denounced France's lenient policy on political asylum, although French President Francois Mitterrand has defended the policy and said "repentant" extremists fell into a different category than "implacable terrorists."

French officials said that in many cases, Italy failed to provide sufficient proof of crimes when submitting the extradition requests.

West German police have complained that their French counterparts lack sophistication in both investigating methods and equipment, shortcomings that have hampered efforts to curtail cross-border terrorism. But last week, France and West Germany agreed on closer coordination to blunt what Chancellor Helmut Kohl called "the new scourge of civilization."