Students of a secondary school said they mourned former state leader Jiang Zemin's death with a heavy heart on Tuesday morning.

Pupils of Scientia Secondary School at Ho Man Tin gathered in a hall to observe three minutes of silence at 10am, after the school gave an introduction to Jiang and played a short video to commemorate him.

The principal, Wong Ching-yung, said he hopes students identify as being part of the Chinese nation and will contribute to the country.

One pupil, Titus Chan, said he was impressed by Jiang's sense of humour and vivacity, adding that his spirit to serve the country was worth learning.

"I know clearly that before I was born and [Jiang] retired, the Chinese Communist Party leader contributed to the prosperity, stability and long-term development of Hong Kong and the country," he said.

"We didn't mourn in silence just for the sake of it or to comply with the Education Bureau's guideline. We knew in our hearts the meaning and why we mourned."

Another student, Kate Leung, said she was also saddened by Jiang's death, saying she had heard about his contribution to the country from her parents when she was younger.

"It's a great pity and I will miss him. My parents had told me... how much he valued Hong Kong and Macau," she said.

Meanwhile, management of the MTR Corporation also observed three minutes of mourning in silence on Tuesday, with flags flying at half staff at the firm's headquarters.

A live broadcast of the memorial service for Jiang was arranged at some MTR malls, while messages expressing condolences were put up on electronic display panels at station concourses.