The High Court of Malaysia has ruled that the detention of a Singaporean man three years ago was illegal.

Mr Wong Chun Khuen, 63, a retired engineer, was arrested by Malaysian immigration officers on Feb 28, 2018, for allegedly harbouring six illegal immigrants.

Under the Malaysian Constitution, he was required to be produced before a magistrate within 14 days of his arrest, which was by March 12 that year.

Instead, he was detained for 29 days and produced before the court only on March 26.

Mr Wong later pleaded guilty before a court in Johor Baru for immigration offences, and was fined RM30,000 (S$9,740) or six months' jail in default.

He owned the house in Johor Baru where the six illegal immigrants were staying, and was arrested when he was at the premises purportedly to carry out repair works.

Mr Wong filed a suit with the Malaysian High Court in 2019 through his lawyer, Mr Arun Kasi. It was alleged that Mr Wong's constitutional rights had been breached by the Malaysian immigration authorities.

On Tuesday, the Malaysian High Court declared his detention unlawful as Judge Noorin Badaruddin granted the declaratory relief sought by Mr Wong.

He is also a client of Singapore lawyer M. Ravi, who worked with Mr Arun to file the suit. In a Facebook post on Tuesday, Mr Ravi said the ruling has come as a huge relief for Mr Wong.

Mr Arun said that while no damages have yet been sought for the wrongful detention, the ruling allows for Mr Wong to file a civil action for damages in the future.