A spate of new bombings in West Germany has aroused government fears that left-wing terrorists are escalating their violent campaign to strike innocent civilians and not just military and industrial targets.

A shadowy leftist group called the Revolutionary Cells claimed responsibility today for three bomb blasts at mining and shipping offices. In a letter to a West German news agency, the authors said they aimed the bombs at "gravediggers" who collaborated with "British coal mining capitalists."

The attacks damaged a miners' union building in Bochum, a coal mining firm's office in Essen and a Hamburg shipping company that exported coal to Britain during the year-long miners' strike there. Nobody was injured.

On Thursday, a bomb exploded in a major department store in Dortmund, wounding nine people, two seriously. An anonymous caller phoned the mass circulation daily Bild to say the Action Christian Klar was responsible and warned of further attacks.

Christian Klar, the alleged leader of the left-wing Red Army Faction, is awaiting trial for murder in a Stuttgart jail. He staged a hunger strike for nearly two months with 30 other jailed terrorist suspects to press demands that they be held together. Their fast, which instigated bombings and arson attacks by supporters, was abandoned Feb. 1 after Red Army Faction guerrillas murdered Ernst Zimmermann, a leading arms industrialist, near Munich.

Since the shooting, police have intensified security for leading politicians and business figures, and have deployed paramilitary forces from the 20,000-strong border patrol to guard potential targets.

The past two days' bombings, the first serious left-wing guerrilla attacks since the Zimmermann slaying, have evoked anxiety here because police fear that the terrorists may now be so desperate that they are prepared to set off random bombings.

Wighard Haerdtl, an Interior Ministry spokesman, said a "new form of terrorism could be developing" through attacks on civilian areas. He said if the perpetrators of the latest bombings prove to have Red Army Faction connections, it would indicate that the terrorists have given up their previous "ideological justification" of striking only at "enemies" such as NATO or arms industry targets.

No more than 20 to 30 left-wing terrorists are said to be active in West Germany, but their isolation may be driving them toward increasingly desperate acts, police officials said.

In recent weeks, European governments have stepped up cooperation among their law enforcement agencies to thwart cross-border connections between left-wing terror groups like the Red Army Faction, France's Direct Action and Belgium's Fighting Communist Cells. All three groups have declared that they were joining forces in an "anti-imperialist" alliance.

In Greece, police are taking seriously a statement purportedly issued by local terrorists who tried to bomb the West German Embassy in Athens last week that they, too, were linking up with the other European left-wing extremists.

On March 2, police found and defused a time bomb outside the West German Embassy in Athens. A movement calling itself the Revolutionary Group of International Solidarity Christos Kassimis printed a 1,000-word statement of responsibility that was found in central Athens after telephone calls to press agencies.

The letter expressed full support for the jailed West German terrorists.