The police are investigating all angles in the case of missing activist Peter Chong, including his medical history.

"We are still investigating the missing persons report. It is a missing persons report.

"We are looking into it (his medical history), we will check," Kuala Lumpur police chief Amar Singh told Malaysiakini when contacted this afternoon.

In another news report, Amar also said the police are checking if there is a link between this case and the abduction of pastor Raymond Koh, who has been missing for more than 50 days.

Chong's son, Darryl, had reportedly said he last saw his father at their house in Kuala Lumpur last Wednesday, and the family lost contact with him a few days later.

The family lodged a police report on Saturday.

Strange encounter

Chong, a former aide to Subang MP R Sivarasa, is the fifth person involved in political or religious activities to have allegedly gone missing since November.

The other four are Koh, pastor Joshua Hilmy and wife Ruth and Perlis Hope activist Amri Che Mat.

Chong's last Facebook post before he disappeared detailed his "strange" encounter with a young motorcyclist on March 31.

"He said he recognised me, that I like to go for protests and candlelight vigil.

"I asked where is he from? I was a little worried and looked around but there were no one else around.

"He said he supported what I do. He said 'but be careful... now there are many people suddenly disappearing. They know where everyone lives," said Chong in the Facebook post.

Chong said when he queried who the man was, the latter only told him to be savvy (pandai-pandai) before riding off.