Police on Saturday rescued two groups of hikers near Sai Kung, as heavy rain fell over Hong Kong, particularly in the east.

Officers said a group of 11 mainland tourists, including seven children, contacted police at about 11.30 am, after finding themselves stranded at High Island Reservoir East Dam. They had previously been camping in the area.

At about the same time, rescuers were also called in by four local hikers who found themselves in difficulty on section two of the MacLehose Trail.

The force said they were able to locate all of the stranded hikers, and evacuate them, adding that none of the 15 were injured and that they didn't require hospital treatment.

The Observatory issued the first Red Rainstorm Signal of the year just before 9 am, before saying it was considering issuing the higher Black Rainstorm Signal at around noon.

At 10.30 am, the forecaster also issued a Landslip Warning, reminding people to stay away from steep slopes, and to stay at home.