Police believe that a serial killer may have been responsible for the murder in Athens yesterday of a prostitute, the second sex worker to be found dead in the city in just a week. The 57-year-old Ukrainian woman had been stabbed at least four times in the neck and chest at a brothel in the center of Athens. The unnamed victim was on her own at the time and the attacker stole her money, police said. A 60-year-old woman had been murdered in exactly the same way in another Athens brothel exactly one week earlier and police said they are linking the two incidents. Officers said they are not discounting the possibility that the attacker killed the women for their money but it seems likely that he may have murdered them for pleasure. In an unrelated incident, a 50-year-old pharmacist was found strangled to death in her pharmacy in the northeastern suburb of Gerakas in what police are treating as a robbery. It was not clear how much money had been stolen.