The woman was found in a pond in Waterfall Bay Park on Monday and pronounced dead at the scene, with police later saying she suffered head wounds.

The victim was a domestic worker who was not employed by the suspects, police said.

A 34-year-old foreign man was arrested a day later along with his wife, a 36-year-old from Hong Kong, when they returned from mainland China.

The man was identified as a British businessman by Hong Kong's South China Morning Post. The British consulate did not immediately respond to an AFP query about the case.

The woman's death was classified as murder because "the evidence did not appear to suggest a natural death", police superintendent Sin Kwok-ming previously told reporters.

An initial post-mortem examination "detected injuries on her head and the cause of death was asphyxiation by drowning", police added.

Police said the two suspects went to the waterfall together on Sunday night but after half an hour the man left alone.

He did not contact the police and immediately left Hong Kong, which superintendent Sin described as "unreasonable" moves.

Authorities said the male suspect, who is due in court Friday, held a Hong Kong ID card but did not give his name or specify his nationality.

His wife was arrested for assisting offenders and released on bail, on the condition she reports to a police station in November.

There are more than 350,000 migrant domestic workers in Hong Kong, with many coming from Southeast Asian countries such as the Philippines and Indonesia.

The Asian Migrants Coordinating Body, an advocacy group, expressed its "deepest sorrow and anger" over the case on Wednesday.