LONDON — More than 100 demonstrators are believed to have been killed across Iran since leaders ordered security forces to stamp out protests triggered by fuel price rises, Amnesty International said Tuesday. “At least 106 protesters in 21 cities have been killed, according to credible reports,” the London-based rights group said. It added that “the real death toll may be much higher, with some reports suggesting as many as 200 have been killed.” The rights watchdog said the security forces…