Police are appealing for information on the whereabouts of 76-year-old Mr Ng Kang Leng @ Wong Kang Leng.
He was reported missing within the Central Catchment Nature Reserve since Saturday, Sep 5, at about 6.52pm.
Mr Ng's last reported location was at the Eco-Link bridge near the Bukit Timah Expressway at about 3pm, walking in the direction towards MacRitchie Reservoir.
He is described as 1.67m tall and has short grey hair. He was last seen in a light blue shirt and black pants, and was carrying a black backpack.
Police trackers and officers from Tanglin Division are involved in the ongoing search and rescue operations with the assistance of PUB and NParks officers.
The police have requested anyone with information to call their hotline at 1800-255-0000 or submit information online at www.police.gov.sg/CrimeStopper.
Trekkers, cyclists and runners in the area are also advised to keep a lookout for the missing man.