One of about two dozen jailed leftists and terrorists on a hunger strike in West German prisons died in Hamburg today after refusing food for nearly 10 weeks, authorities said.

Several hours after the announcement of the death of Sigurd Debus, 38, a lawyer representing the striking prisoners said they had decided to break off their protest on the understanding some of their demands for better prison conditions and the privilege of being held in groups rather than in separate cells would be met.

Debus, who had been sentenced to 12 years in jail for robbery and attempted bomb attacks, had been on strike since Feb. 11. Although he was carrying on his strike to support demands of the others for improved treatment, Debus had never had close contact with either the Red Army Faction or its splinter group, the June 2 Movement.

Moreover, he had a radio and television in his cell and never was isolated from other prisoners, so he already had the conditions the others were demanding.

West German authorities voiced fear of violent reaction to the death of Debus by sympathizers and terrorists still at large. Although there have been no major attacks by West German leftist urban guerrilla groups since 1977, a series of bomb and fire-bomb blasts lately -- as well as four attacks on trains this week when power lines were short-circuited or obstacles thrown across the tracks -- have been linked by police to sympathizers of the hunger strikers.

A bomb was discovered today at the U.S. Air Force base at Wiesbaden and defused, according to a military spokesman there. The spokesman said leaflets on the scene were found that read: "Death to the Americans. This is revenge for our comrade who died for the cause." Explosives experts reportedly defused the nine-pound bomb, which was found by a passer-by hanging from a six-foot rope from the roof of the Wiesbaden military community center.

About 500 people rampaged through the center of West Berlin last Sunday smashing windows and looting shops following a rumor that Debus had died. Two days ago, Frank Dahrendorf, the West Berlin senator responsible for the city's internal affairs, said West German security officials believed the death of any of the striking prisoners could set off murder attempts against politicians and judicial figures, reminiscent of the killing in November 1975 of West Berlin Chief Judge Gunther von Drenkmann the day after terrorist Holger Meins died in a similar hunger strike.

West Berlin Mayor Hans-Jochen Vogel today issued an appeal not to use the death of Debus as impulse for new acts of violence.

Approximately 24 to 28 imprisoned leftist West German terrorist and their sympathizers have been on a hunger strike that began on Feb. 2 with nine prisoners in West Berlin's Moabit Jail and Stuttgart's Stammheim Prison, then spread to jails in eight other cities.

Justice authorities had refused to give in to the strikers' demand that prisoners sentenced for terrorist crimes be held together in groups of 10 or 15, regarding this as part of a strategy to organize escapes. The prisoners, in turn, had rejected an offer that would have allowed them to mix with prisoners sentenced for other crimes.

West German Justice Minister Jurgen Schmude, replying to an appeal this month by Amnesty International, said in a letter released in Bonn today that separate measures could be taken to improve the conditions of the prisoners providing they stopped the strike.

Apparently in veiw of this letter, the strike was called off today.

A declaration released in Hamburg by attorney Peter Tode on behalf of the prisoners said: "We have reason to assume that after interventions on the part of Amnesty International, no prisoner will be kept in isolation any more and several groups of prisoners will be formed."

Eight or nine of the striking prisoners were reported to be in critical condition and several were said by the West German news agency to be receiving force-feeding.

Hamburg's judicial authorities said today that all possible steps had been taken to try to keep Debus alive, but that he had refused medical treatment. An offical statement said, "Medical help has its limits if a person is prepared to die."