More than 100,000 Taiwanese people took to the streets Saturday in protest over the death of a young conscript who was allegedly abused in the military.

Singing a Taiwanese take on the revolutionary song "Do you hear the people sing?" from the hit musical "Les Miserables", protesters rallied at a square near the presidential office in Taipei, mostly dressed in white -- a colour symbolising truth in local culture.

It was the second mass protest since Corporal Hung Chung-chiu died of heatstroke on July 4 -- apparently after being forced to exercise excessively as punishment for taking a smartphone onto his base -- just three days before the end of his compulsory year-long military service.

About 30,000 people demonstrated outside the defence ministry in the capital on July 20, according to Citizen 1985, an activist group that organised the protests.

"We estimate a bigger turnout today on the eve of Hung's funeral than the previous protest. We hope the government will hear the people's anger at its handling of the case," Liu Lin-wei, a spokesman for the group, told AFP.

"I want to thank everyone for your efforts and I hope we can have truth and justice for Chung-chiu with all your help," Hung's mother told the crowd.

Organisers claimed 200,000 people joined the protest, while the government's estimate of the crowd size was 100,000.

"I am mourning for Hung Chung-chiu and I want the truth. I hope there won't be any more abuse and death like his in the military," said protester Jenny Tan.

President Ma Ying-jeou has apologised for the incident and vowed to seek justice for the victim and punish those responsible.

"The cabinet has requested the defence ministry and the justice ministry to spare no effort to investigate the case and review the current system to prevent any unhumanitarian actions and abuse of power," Premier Jiang Yi-huah told reporters.

He also promised to meet the activist group's demands to set up a committee to probe military wrongful imprisonment cases and to review the military tribunal system.

Amid mounting public anger, defence minister Kao Hua-chu stepped down earlier this week, while 18 military officials have been charged over Hung's death, including the former commander of his brigade.

They were indicted on charges ranging from abuse leading to death and involuntary manslaughter to imposing illegal punishment on a subordinate and offences against personal liberty, according to military prosecutors.

The 24-year-old had been subjected to exercises that were "unbearable, cruel and abusive", resulting in his death from multiple organ failure triggered by heatstroke, prosecutors said.

He was sent to solitary confinement and ordered to do the exercises as a punishment for bringing a camera-phone to camp and for defying his superiors on some duty assignments, according to the indictment.

Hung's family said he was repeatedly refused water during the punishment despite being close to collapse and that he had previously filed complaints about other abuse meted out by superiors.

Prosecutors did not specify what jail terms they were seeking. Legal experts say the most severe charge is of abuse leading to death, which is punishable by life imprisonment.

Citizen 1985 has criticised the indictment as "hasty and sloppy", saying only one sergeant was charged with fatally abusing Hung, while other higher ranking officers were indicted with lesser charges.

Analysts have said Hung's death has dealt a blow to the defence ministry's plans for a professional military.

The ministry wants to phase out its decades-old compulsory 12 months of service by the end of 2015, replacing it with four months of military training for men aged over 20.

The government hopes volunteers will then enlist for a longer period of military service, making for a better trained, more highly skilled military.

Taiwan currently has around 275,000 service personnel among a population of 23 million, down from a peak of 600,000 during the Cold War.

In the six months to June the military recruited just 1,847 people -- 31 percent of its target of 5,887. The defence ministry had planned to recruit 17,447 people before the end of February next year.