Jakarta: Indonesian police have arrested a factory owner and four foremen for allegedly torturing workers and illegally confining them, an official said on Sunday.

Factory owner Yuki Irawan and the four were accused of “torturing and depriving the personal freedom” of 34 workers, after a tip-off led to a raid Friday on the illegal aluminium pot company in Tangerang city outside Jakarta, said city chief detective Shinto Silitonga.

The male workers, including four 17-year-olds, were forced to work at least 16 hours a day with only two meals a day and no pay, for between two months and one-and-a-half years, he said.

“They told us they were slapped, kicked, pushed, burned with cigarettes and had hot water poured on them if they disobeyed,” he said. “At night, they were locked in an eight-by-six-metre room and forced to sleep on concrete floor and thin mats. They had no way to escape.”

The workers have since returned to their hometowns, he said.

“They were dishevelled, their clothes were tattered, their skin was covered with bug bites and rashes, some were really skinny,” he said. “They were also fearful of people.”

Despite fears that wage increases will encourage businesses to move to neighbouring countries such as Vietnam, Indonesian factory workers remain some of the lowest-paid in Asia, often earning less than workers in China or India.

Around 55,000 workers gathered in Jakarta for the May Day rally, the biggest the capital has seen in recent years as south-east Asia’s biggest economy booms.

Labour activists say the number of protesters has swelled this year as anger grows at businesses denying many workers their basic rights, with poor salaries and a lack of benefits for those who are not employed full time.