Hong Kong  - Three teenagers were arrested after a 13-year-old boy was injured when a homemade bomb exploded, a media report said Sunday.

The three, including the injured boy, were held by police for possessing explosives favoured by Islamic terrorists, the South China Morning Post said.

Police suspect the classmates of a Kowloon Tong district school learned how to make the explosive triacetone triperoxide (TATP) powder on the internet.

The same powder was used in the London terrorist blasts in July 2005, and TATP was one of the explosives used by so-called US shoe bomber Richard Reid, the report said.

The teenager sustained injuries to his face, an eye and two fingers after igniting a fuse attached to two plastic bottles containing the explosive shortly after midnight yesterday. The youth was taken to hospital after his mother called police following the explosion.

Police later went to the home of a 14-year-old friend who was also arrested after officers found six more bottles of the explosive and seized a computer.

Officers detained another 13-year old who had been given bottles of the explosive.

Initial police investigations show the 14-year made the explosive for fun after he bought the necessary chemicals from local shops when he learned how to make TATP online.

The trio were later released on police bail.

University of Hong Kong chemistry professor, Fung Ying-sing, said videos of how to make explosives using TATP can be easily found on the internet.

"It is difficult to control online information about making explosives, and it is really dangerous to make them without guidelines. One can set off an explosion with just a few grams of TATP," he said. (dpa)