Police said the bombs found Monday evening inside a high school on Hong Kong Island were "complete, fully functional and ready to be used."
The origin of the bombs was not clear. The Wah Yan College said the bombs were found in a public area of the school and that there is no evidence linking them to any of its staff or students.
Police said the bombs were radio-controlled, to be triggered with mobile phones. They contained 10 kilograms (22 pounds) of high explosives and shrapnel that would inflict injury. Their blast could have been felt over a distance of 100 meters (yards) or more, police said.
Alick McWhirter, the police explosive squad's senior disposal officer, said that had the bombs exploded, they could "have killed and injured large numbers of people."
In July, police announced the seizure of about 2 kilograms (4.4 pounds) of TATP, which has been used in militant attacks worldwide. Other recent seizures in Hong Kong involved far smaller amounts, just 1 gram, of TATP, or tri-acetone tri-peroxide.