Police have arrested a 24-year-old man in connection with the recent sex-worker murders.

With the help of Macau Judiciary Police, Hong Kong officers arrested the suspect at the Hong Kong-Macau Ferry Pier in Sheung Wan early this morning and found two mobile phones belonging to the victims.

Police believed the man is related to the series of sex-worker murders and in-depth investigations are ongoing.

The four murders - one in Yuen Long, one in North Point and two in Tai Po - took place on March 15 and 17.

At about 2.20pm yesterday, a woman found her 27-year-old female friend collapsed in a flat on Electric Road in North Point and called Police.

Officers found the 27-year-old unconscious inside the toilet with her forehead swollen and lower jaw injured. The woman was certified dead at the scene and a post-mortem will be conducted today. 

Three other women, aged 31 to 35, died in their flats on March 15 and 17.

At about 1.10am on March 15, a 74-year-old man called Police to say he thought his 35-year-old wife had collapsed inside a flat on Tung Lok Street in Yuen Long. Police found the woman lying unconscious in the bathroom with a hose around her neck. The flat had been ransacked.

At about 10.15pm on March 15 Police found a 31-year-old woman collapsed inside a flat on Wai Yan Street in Tai Po after receiving a report from her friend. Her purse had been looted. She was sent to the Alice Ho Miu Ling Nethersole Hospital where she was certified dead.

At about 12.45am on March 17 a woman who had lost contact with her 35-year-old female friend called Police. Officers found the friend unconscious outside the bedroom of a flat on Kwong Fuk Road. She had no apparent external injury and the flat had been ransacked.