Witnesses said fire fighters and airforce helicopters were still trying in the early afternoon (0815 GMT) to put out the blaze and rescue an unspecified number of people stranded inside.
Army, police and the elite Rapid Action Battalion force had joined the rescue effort.
The cause of the fire and extent of damage caused was not immediately known.
Witnesses said thousands of people thronged the roads around the 11-storey building more than four hours after the blaze started.
"The fire is still raging inside," a fire-fighter said, as thick smoke billowed into the sky.
The building, in the Kawranbazar business district of Dhaka, houses NTV and Rtv stations and the Amar Desh newspaper, all owned by a former member of parliament.
Survivors said around 2,500 people work in the building on normal work days.
The building also houses at least half a dozen other commercial and business offices.