The transformer explosion also plunged the area into darkness, making escape more difficult.
"There were screams, shouts for help and total chaos," Kalam said.
Fire official Abdus Salam said firefighters were delayed because their vehicles couldn't fit through the narrow streets and there was no nearby source of water.
Firefighters and residents carried victims to hospitals on three-wheeled rickshaws as relatives wailed.
The state-run Dhaka Medical College Hospital was overwhelmed with burn victims. Burn unit chief Shamanta Lal Sen said it was the worst disaster he had seen in his 40-year career.
Government administrator Mohibul Haque said 116 people were confirmed dead. The death toll could increase because some people were still feared trapped in the rubble, he said.
Bangladesh will hold national mourning for the dead Saturday when flags are to be flown at half-staff and special prayers to be held at places of worships across the country.
Businessman Mohammad Gulzar was serving beverages to dozens of guests who had just arrived in his small apartment for his daughter's wedding reception when they were jolted by a loud explosion. The building was quickly engulfed by fire, and the guests tried to run outside but could not because the blaze already covered the gate of the five-story building.
At least 15 of Gulzar's guests and family members were trapped and died.
"Why me, Allah? What wrong have I committed?" Gulzar, 50, cried as he sat in front of rows of corpses covered with white shrouds on the road outside his burned apartment.
Gulzar's daughter Runa Aktar survived because she was at a beauty parlor to prepare for the ceremony.
Mohammad Faruk, who lived nearby, lost all 16 family members -- his wife, children, grandchildren and parents.
Many of them normally would have been at work, but on Thursday night all came home early because of the heavy rain.
Faruk, however, had to remain at work late because of a business deal and was the only one who survived.
"I should have come home early," he said, sobbing. "Maybe I could have saved some of them."