Some women dentists practising in North Goa's Calangute belt have received letters "signed" by slain IS founder Abu Musab al-Zarqawi, demanding between Rs 1 to 2 crore as "protection money", the police said today. The Calangute belt is known for "dental tourism". Prima facie, around five dentists have received such letters in the recent past, though the police have refused to divulge the exact number. "Some women dentists practising in the Calangute belt of North Goa have been receiving the letters signed off with Abu Musab al-Zarqawi's name, which are being examined. "The letters demand protection money between Rs 1 to 2 crore. Formal complaints have been lodged with the police and we are investigating them," Calangute Police Inspector Jivba Dalvi told PTI. You May Also Like To Watch: Abu Musab al-Zarqawi is believed to have been killed in 2006. The officer said police have taken all preventive measures and stepped up security outside the clinics of the complainants. Dalvi didn't specify the number of such complaints received by police and the exact nature of the threat given to the dentists concerned in these letters. However, one of the complainants the PTI spoke to today has claimed that at least four more dentists in the area, besides her, have received such letters over a period of time. According to the sources in the police, one of the dentists had filed a complaint in May and again earlier this month. Similarly, some more women practitioners too have received such letters, they said. Police have registered a case under section 507 (criminal intimidation by an anonymous communication) of the Indian Penal Code. The sources said the letter asked a complainant to hang a white coloured cloth outside her clinic if she was ready to pay the money. "In a bid to trap the sender, she did put up a white coloured cloth, but nothing happened. Later, she received another letter raising a similar demand," they said. The dentist said she received the second threat letter only last week. "Both the letters I received had identical handwriting, though their content was slightly different," she said. She claimed at least four dentists from Calangute area have received such letters apart from her. "One of the dentists practising in Calangute and also in Mumbai had received a similar letter, following which\u00a0she filed a complaint with the Mumbai Police. There are three more dentists who have received such letters in this area," she said, adding she was getting the support from local police. Dental tourism is flourishing in Goa. Tourists, mainly foreigners, prefer getting their dental treatment done here as the expenditure is comparatively less than in their home countries.