The Dutch sweets giant behind the Mentos and Alpenliebe brands has pledged to investigate after its workers in Bangladesh said they were attacked, just weeks after setting up a union.
The new trade union's general secretary Kamrul Hasan said about 20 unknown attackers wielding sticks entered a factory run by Perfetti Van Melle earlier this week and beat him up.
A spokeswoman for the company, which has its headquarters in the Netherlands, expressed regret over the incident and said it had taken steps to protect workers.
"Securing the safety of our employees at work is our responsibility," Saskia Huuskes told the Thomson Reuters Foundation by email.
"We are investigating the incident and we have taken measures to protect the safety of all employees in our factory."
The rights of workers in Bangladesh, a global manufacturing hub, have come under increased scrutiny in recent years, particularly since the Rana Plaza factory collapse in 2013 that killed 1,100 people.
Workers at the factory in Gazipur, near the capital Dhaka, said they had earlier received threats over their plans to unionise, and accused local managers of inaction over the attack on Tuesday.
"They entered the factory and threatened everyone. They beat me up in front of company officials and no one did anything," said Hasan.
The incident was reported to police, who said it had been a fight between two groups of workers in the factory, contradicting Hasan's account.
The union's president Kamrul Hasan Palash said the company's local managers had opposed the formation of a union for the factory's 250 permanent workers.
"After we formed the union, we applied to the ministry to get it registered as per the law," he said.
"When the management came to know about this, they did not allow me and four others to enter the factory for five days. I was threatened."
Perfetti Van Melle said it adhered to local labour laws, which allow for the formation of unions.
"A workers union was established and approved by the relevant authorities by the end of February this year," Huuskes added.
The company, which has operated in Bangladesh since 2004, said it was still building a relationship with the union and had provided training for workers on their rights.
The union has submitted a list of demands ranging from better-quality food in the canteen to higher pay.
"I have been working here for 10 years and yet my salary is just 13,000 taka ($155) per month. This is just one of the issues that we want to talk about. And it's something that we can do now, because we have a union," said Palash.
Managers at Perfetti Van Melle held talks with workers on Thursday to try to address staff concerns over the incident.
Experts say Bangladesh's record on workers' rights has improved since the Rana Plaza disaster, which put its garment industry under the global spotlight.
But progress in other sectors has been slower, said Amirul Haque Amin, head of the National Garments Workers Federation.