SEOUL (AFP) - A former Seoul police chief and three other officers were charged on Tuesday (Oct 17) over the death of a protester hit by a water cannon during an anti-government protest two years ago.

Baek Nam Ki, a 69-year-old farmer, was knocked over by the jet of water during a huge protest against Seoul's labour policies in November 2015, and fell into a coma. He died 10 months later.

His plight sparked widespread outrage, with police coming under fire for what critics described as excessive force during public rallies.

Goo Eun Soo, the city's police chief at the time, another official and the two officers manning the water cannon were charged with negligent homicide, the Seoul Central District Prosecutors' Office said.

Police allegedly trained the jet squarely at the victim's head, despite a ban on directing it above the chest.

Prosecutors also revealed that a device controlling the water pressure was malfunctioning, enabling it to be used at pressures exceeding the legal limit.

Police have denied responsibility for Baek's death, saying they followed all applicable rules.

The case was reopened after new president Moon Jae In took office in May. Alleged excesses under the government of ousted president Park Geun Hye have been coming to light.