They were joined by workers from other factories in the area as they occupied the road stretching from Mirpur 10 to Mirpur 14 in protest from around 7:30 am Tuesday, law enforcers said.
"Thousands of workers are demonstrating for their wages and allowances, making the road completely impassable," said Kafrul Police Inspector Jahanur.
Asked about the matter, Monirul Alam Shuvo, chairman of BGMEA's PR standing committee, said they were aware that workers of Opex Group's factory had taken to the streets in protest.
"We still don't know if they have been joined by workers from any other factory. There's a lot of misunderstanding about wages and bonuses in many quarters. Workers are protesting too."
bdnews24.com could not immediately reach the authorities of Opex for comment.
"The demonstrations are mainly being led by workers of Opex Group. They have been joined by workers from a few other factories. We've also received information that the protesters hurled brickbats at some factories," said Additional Deputy Commissioner Mizanur Rahman.
Businessman Anisur Rahman Sinha is currently overseeing Opex Group's operations as its managing director. Apart from Mirpur 13, the group also has garment manufacturing units in Narayanganj's Kanchpur, Shiddhirganj and Savar's Ashulia.
The factory authority had earlier held a meeting with government officials and workers' representatives in which they agreed to pay the salaries for May within the first week of June, said a BGMEA official, asking not to be named.
They also decided to give the workers a three-day holiday to limit their travels during Eid-ul-Fitr and pay them half their bonuses immediately with the remainder to be paid up later, depending on the company's financial position.
"Previously, it was decided that the factory would also pay its absentee workers 60 percent of their wages for April. As far as I know, most garment factories have cleared their salaries for April. But now the problem lies with the payment of wages and bonuses in May," the anonymous official said.
Most factories are paying 50 percent of the bonuses but there are a few that have paid their workers in full, he added.