More than 50 other people were injured, many of them critically, bdnews24.com reported.
Rescue workers were still searching for possible survivors or more bodies Sunday morning, the news website said.
"We are confirmed about 11 deaths," Chandgaon Police Station Officer-in-Charge Babul Chandra Bhowmik told bdnew24.com.
Shah Haji Mohammad Bokhtiar, owner of the Shah Amanat Decorators, located beside the flyover, told bdnews24.com he saw three girders collapse "one after another."
"It appeared to me that at least 60-70 people are still trapped under the debris," he said.
At least a dozen more people were hurt when a nearby mosque wall collapsed after hundreds climbed on top of it.
Police also fired several rounds of tear gas when people upset about the accident started demonstrating in the vicinity. Several vehicles were vandalized and at least 10 motorcycles were torched, bdnews24.com said.