All six are undergoing treatment at Sheikh Hasina National Institute of Burn and Plastic Surgery in the capital.
The incident took place near a tea stall in Sayedabad around 5:00pm on Saturday.
Injured Shamsuddin Robin said they sustained the burn injuries when a gas cylinder exploded near a tea stall in Sayedabad Janpad crossing area of Jatrabari, while painting a cylinder. After being rescued, they were rushed to Sheikh Hasina National Institute of Burn and Plastic Surgery.
Ayub Hossain, a resident surgeon at the Institute, said Kabir Hossain sustained 85 per cent burn injuries, Abul Kalam received 80 per cent, both Shamshuuddin Robin and Shafiqul Islam received 78 per cent and Md Ripon received 60 per cent burn injuries. Bishwanath Datta received 38 per cent burn injuries.
The condition of the first five is critical, while Bishwanath Datta is out of danger, Ayub Hossain said.
Inspector Bachchu Mia, in-charge of police camp at Dhaka Medical College Hospital, confirmed the matter.