SINGAPORE - People's Action Party (PAP) Bukit Batok MP David Ong, who resigned suddenly on Saturday (March 12), is believed to have had an extramarital affair with a woman who is a grassroots activist in his ward.

The woman is understood to be Ms Wendy Lim, 41, who works in a logistics firm.

Photographs of her participating in grassroots activities in Bukit Batok and supporting the party during last September's General Election were posted on a Facebook page titled Bukit Batok PAP Woman's Wing. Some showed her with Mr Ong.

Channel NewsAsia reported on Saturday night that the affair is believed to have gone on for about six months, "and came to light after the woman's husband complained about it".

Lianhe Zaobao's website reported that Ms Lim was an active member of the PAP's Women's Wing in Bukit Batok, and that she was active in grassroots events. It said Ms Lim also posted photos of her and Mr Ong taken at Keming Primary School during the elections last year.

Mr Ong, 54, had earlier said that he was stepping down due to "personal indiscretion". He said: "There is personal indiscretion on my part which I deeply regret. I would appreciate if you can give me and my family the privacy to heal and rebuild."

A by-election will be held for the Bukit Batok single-seat ward, said Prime Minister Lee Hsien Loong.