Residents in South Africa's city of Cape Town have been asked to keep a look-out for a renagade young hippopotamus which is popping up in gardens and roads after moving into a suburban lake.

City officials are hoping the two-year-old calf will return back to its pod after appearing in an unfenced reserve following the theft of part of the boundary fence in the neighbouring water body where it lives.

"The night before last he was in peoples' gardens, obviously there were lots of people out," Julia Wood, manager of Biodiversity Management told AFP. "And then last night somebody picked him up on one of the roads."

The city will monitor the animal for two weeks but is considering capture or darting if he does not leave Zeekoevlei, which is in the densely populated Cape Flats area.

"The public is advised to be particularly cautious, as hippos are known to be extremely dangerous wild animals," the city said in a statement, urging residents and users of the lake not to approach the animal or stop it.

"This could lead to dangerous encounters and may potentially prolong the capture operation by influencing the animal's behaviour. Motorists in the area of Zeekoevlei should be cautious."

The animal is believed to have followed a female hippo who gave birth. The new mother and baby returned to their usual ground but the young hippo, whose sex is unknown, remained behind.

The city has six hippos in the False Bay Nature Reserve and residents have been asked to report any sightings. The name of Zeekoevlei comes from the hippos who used to live there before being near hunted out by the 1700s.