Two bomb hoaxes, one claimed by a leftist group, caused upheaval in central Athens and the northern suburbs yesterday. The first hoax began at 11.15 a.m. when an anonymous caller telephoned the Hilton Hotel in downtown Athens and warned that a bomb had been planted on the grounds and would go off within 25 minutes. The caller said that the leftist group Popular Revolutionary Action had planned the hit. Police evacuated the hotel and cordoned off the area. But a search by officers failed to unearth any suspect device. The second hoax occurred a few minutes later. An anonymous caller contacted police at 11.30 a.m. to warn that a bomb had been planted at the Neo Iraklion station of the urban electric railway, in northern Athens, and would detonate within the hour. The station was evacuated and train services suspended as bomb disposal experts searched for a device. Again nothing was found. There had been no claim of responsibility for the second hoax.