Sukhwinder Singh, 31, was chasing after thieves who had snatched a woman's handbag in Barking when he was stabbed in the heart.

He was leaving Barking station on January 8 when he saw the 28-year-old woman being mugged.

The teenagers arrested are being held at an east London police station, Scotland Yard said.

Three other men arrested by police on January 13 were released on bail pending further inquiries.

Mr Singh, of Harts Lane in Barking, died in the Royal London Hospital after the incident in Uphall Road.

:: Anyone with information was asked to call the incident room on 020 8345 3775 or Crimestoppers on 0800 555 111.