West Germany's most notorious terrorist group, the Red Army Faction, has acquired substantial sums of money, weapons and explosives and seems poised for a more ruthless offensive against U.S. and allied military targets in Europe, police and security officials said.

The latest spate of violent attacks in West Germany has alarmed authorities because the terror tactics have aimed at a high death toll and reflect a desire to inflict random casualties. In the past, attacks were limited to military property or prominent individuals such as judges, bankers and industrialists.

The resurgence of the Red Army guerrillas has surprised law enforcement authorities here, who believed the group was close to extinction in 1982 following the arrests of three key organizers and the seizure of major weapons caches.

But the nucleus of the group has doubled to about 20 committed terrorists, who can rely on passive support and shelter from hundreds of sympathizers sharing their anti-NATO, class-warfare motives.

Security and intelligence officials say the guerrillas have rebuilt a formidable arsenal through raids on gun shops and explosives depots.

They have gained possession of nearly 100 guns, including powerful repeater rifles that use fragmenting bullets, and hundreds of pounds of explosives. The Red Army Faction also is believed to have amassed more than $1 million, money stolen from banks or extorted through kidnapings, the officials said.

Moreover, the guerrillas have established close links with radicals in other European countries, such as France's Direct Action and Belgium's Fighting Communist Cells.

But efforts to foil the terrorist network by enhancing cross-border cooperation among European governments have foundered so far.

West German and Italian police have faulted their French counterparts for refusing to pursue suspected terrorists who have found safe haven because of France's long tradition of granting asylum. More than 120 members of Italy's Red Brigades are believed to be living in France. The government in Paris has said many of them are not deemed guilty in terms of French law.

After the murders of French Gen. Rene Audran and West German industrialist Heinz Zimmermann were jointly claimed by the Red Army Faction and Direct Action early this year, the French and West German governments announced cooperative measures to combat terrorism, including the installation of a special "hot line" to exchange information on suspected guerrillas.

But West German officials say they have been disappointed because the French have not shown any willingness to employ sophisticated computers or other modern devices in tracking underground terrorists. As a result, West German police say the terror trail usually goes dead whenever any suspect crosses into France.

The latest terror campaign began last December, when a hunger strike by 30 imprisoned Red Army Faction members triggered a wave of bombings and arson attacks primarily aimed at property connected with the North Atlantic Treaty Organization.

Officials surmise that the jailed guerrillas, who include original ringleaders such as Brigitte Mohnhaupt and Christian Klar, have been able to send out messages through their lawyers to other underground terrorists.

Even so, the direction of the group's operations is said to have passed to three women on the outside: Inge Viett, Sigrid Sternebeck and Silke Maier-Witt. A man, Ekkehard von Seckendorff-Gudent, is also said to be an important voice in planning guerrilla attacks.

The new leadership appears to have been trying to attract new recruits by emphasizing attacks on American and NATO-related targets to exploit lingering dismay over the failure of nonviolent protests to stop the deployment of new Pershing II and cruise nuclear missiles in West Germany.

"The argument they make is that since peaceful action did not stop the missiles from coming, violent methods are now necessary. There are some people, who ordinarily would not be terrorists, who are ready to accept that line of thinking," an Interior Ministry official said.

New members are believed to have assisted in attacks on property, such as the two dozen minor arson and bombing attacks on NATO pipelines. Some explosives and firebombs failed to go off because of rudimentary faults that could be traced to amateur hands, police say.

Last week, cleaning women aboard a U.S. armed forces train discovered blankets drenched in flammable liquid that failed to ignite because a triggering mechanism was botched.

But the recent assassination plots and car bombs have shown a degree of sophistication and technical skills that could only be carried out by trained terrorists, police said.

The slaying of a young American soldier Aug. 8 and the car bombing of the U.S. Rhein-Main Air Base a few hours later, in which two Americans were killed and 20 others injured, demonstrated a more ruthless attitude and a more effective use of explosives than the terrorists have shown in earlier years.

Police are now pursuing the hypothesis that Spec. 4 Edward Pimental, 20, was killed so that the terrorists could use his military identity card to gain access to the air base where the car bomb was planted.