His brother, Tourism Minister Rashed Khan Menon, told bdnews24.com that he had been found dead in his Baridhara residence in the city on Monday.
Sadeque's car driver Nazrul Islam said the veteran journalist went to have a shower at around 11.
As he was not coming out and not responding to calls for long, the washroom was broken open at around 12 noon. He was found dead, he said.
The driver said Menon rushed to the house on receiving the information and sent Sadeque Khan's body to United Hospital.
The 83-year-old journalist is survived by his wife, two sons and two daughters.
Sadeque embarked on a career in journalism in the 1950s. Over time, he wrote columns for different newspapers, including the English weekly Holiday.
He was also involved in the film industry. Nadi O Nari, a film he starred in, was released in the early 1960s.
An adherent of the political ideology of Maulana Abdul Hamid Khan Bhashani, Sadeque Khan announced the establishment of a political party named Bangladesh Ganashakti Dal in 2012.
BNP Chairperson Khaleda Zia, Secretary General Mirza Fakhrul Islam Alamgir and leaders M Shamsul Islam and Tariqul Islam expressed condolence at his death.
Sadeque was the eldest among six children of Abdul Jabbar Khan, whose family hailed from Babuganj, Barisal.
His brother Abu Zafar Muhammad Obaidullah Khan was a secretary to the government. Prominent as poet Abu Zafar Obaidullah, he later served as agriculture minister in the regime of military dictator HM Ershad. Another brother Enayetullah Khan was the founder of weekly Holiday and the English daily New Age. In the late 1970s, Enayetullah Khan served in the government of Bangladesh's first military ruler General Ziaur Rahman. Under the Ershad regime, Enayetullah Khan was Bangladesh's ambassador to China and Myanmar.
Sadeque's sister Selima Rahman is a BNP vice-chairman and was a state minister in Khaleda Zia's government.
Sadeque's brother Menon, president of the Workers Party, is currently minister for civil aviation and tourism. Another brother, Shahidullah Khan Badal, once a contractor, is a director of Dhaka Bank and is on the board of directors of the newspaper New Age.
Now-defunct Daily Azad chief reporter Sheikh Rakib Uddin told bdnews24.com, "He (Sadeque) had a chequered career. He proved his talent not only in journalism, but also in different areas of the film industry."
Secretary General of Bangladesh Federal Union of Journalists' pro-BNP faction M Abdullah, Dhaka Union of Journalists President Abdul Hye Sikder and General Secretary Jahangir Alam Prodhan, National Press Club President Muhammad Shafiqur Rahman and General Secretary Kamrul Islam Chowdhury also condoled the death of Sadeque.
Source: Bangladesh's First Internet Newspaper