"We are observing a mourning day across the country to pay respects to Prof Pisah Karim," Joint Secretary General Ruhul Kabir Rizvi said Friday.
He said the party flag was flying at half-mast and black flag had been hoisted at all its offices across Bangladesh.
"Our activists have sported black badges," Rizvi said, adding that a funeral prayer would be held at the national mosque, Baitul Mukarram, after Jumma prayers.
Although many had dubbed the TV commentator to be an 'agent of the Jamaat-e-Islami' for his controversial remarks, the BNP viewed him as an 'uncompromising person who protested against injustice'.
BNP chief Khaleda Zia had personally visited the bereaved family and offered condolences.
Meanwhile, Karim's body was taken to his Dhanmondi residence from the Square Hospital mortuary on Friday morning for people to pay respects.
His brother Lotus Karim told bdnews24.com that the body had been taken to Baitul Mukarram around noon from there.
Police said they had beefed up security around the national mosque to prevent any untoward incident.