Police on Tuesday arrested two sisters, one 60 and the other 71, who allegedly used a luxury apartment in the Mid-Levels on Hong Kong Island as a call center to operate a suspected vice ring.

Officers from the Organized Crime and Triad Bureau raided a 1,500-square-foot apartment on Tregunter Path and arrested a woman aged 60, who was believed to be the mastermind of the syndicate, and her 71-year-old sister, who assisted in running the prostitution ring, news website HK01.com reported.

Police also arrested two domestic workers who allegedly assisted the operation of the call center in the apartment and arranged work for the prostitutes.

A large amount of evidence, including HK$10 million (US$1.27 million) in cash, share certificates and a car were collected by the police. 

Police said the syndicate operated a website that carried pictures of women who could provide high-quality escort services for a charge of HK$6,000 to HK$7,000 per hour, Apple Daily reported.

The operation allegedly targeted foreign visitors to Hong Kong and claimed that all of its sex workers were students, models or dancers, and listed their personal information on the website.

The website said the services were legal in Hong Kong.

Earlier, three suspected prostitutes from Venezuela and Russia were arrested in a hotel in Tsim Sha Tsui, Kowloon, in the same operation.