Sheikh Hasina launched the celebrations on Monday, first as prime minister and then as Awami League president, by placing wreaths at the Bangabandhu Memorial Museum in Dhaka's Dhanmondi.
Members of her Cabinet and senior Awami League leaders joined her in paying respect to the founder of the nation.
Awami League's affiliate organisations later paid floral tributes to the portrait of the independence hero.
On this day in 1971, Vice President Syed Nazrul Islam had taken oath as the acting president of the provisional government in exile in the absence of Bangabandhu Sheikh Mujibur Rahman.
Tajuddin Ahmad was its first prime minister, M Mansur Ali finance minister, Khondaker Mostaq Ahmad foreign minister and HM Qamruzzaman took oath as the home, and relief and rehabilitation minister.
General Ataul Gani Osmani was appointed as the commander-in-chief of Bangladesh liberation army.
A day after the government was formed, Tajuddin addressed the nation. With it, the world came to know that a government had been formed for a nation in the making.
The skilled leadership of the government-in-exile won the war within nine months, which gave birth to the new nation on Dec 16, 1971.