An MTV employee said a group of around dozen or more persons had arrived in a white van around 2.
00 am, armed with automatic rifles, assaulted security guards, taken away their phones and entered the complex.
Sounds of breaking glass and objects being smashed and a loud explosion had then been heard.
Journalists who entered the complex later also saw unexploded grenades.
By dawn, eyewitnesses said a fire at the station had been put out by the fire brigade.
Updated The MTV broadcasting group which owns the popular Sirasa, MTV and Shakthi television channels as well as a string of popular radio stations had been attacked early hours of Tuesday.
MTV channel head Chevaan Daniel said a heavily armed group had broken into the complex and virtually destroyed its facilities.
The station was struggling to get on air, he said.
The main control room and equipment had been shot at.
Earlier in the week unknown persons lobbed a petrol bomb at the station.