Army chief Waker-Us-Zaman said in a televised address that Hasina, 76, had left the country and that an interim government would be formed. Waker's announcement comes after more than 90 people were killed on Sunday in the deadliest day of violence in anti-government demonstrations that began in July.
Bangladesh's army chief Waker-Uz-Zaman said Monday he would "form an interim government" after the prime minister resigned and fled the capital in the face of overwhelming protests.
"I am taking full responsibility," the general said, dressed in military fatigues and cap, although it was not immediatly clear if he would head a caretaker government.
"We will form an interim government," Waker said in a broadcast to the nation on state television, adding that Sheikh Hasina had resigned.
"The country has suffered a lot, the economy has been hit, many people have been killed -- it is time to stop the violence," he added.
"I hope after my speech, the situation will improve."
He said he would talk to the president to form the interim government and had held talks with the main opposition parties and civil society members -- but not Hasina's Awami League.
Waker is a career infantry officer who has spent nearly four decades in the military, serving two tours as a UN peacekeeper as well as in the prime minister's office.
"If the situation gets better, there is no need for emergency", he said, vowing the new authorities would "prosecute all murders" following weeks of deadly protests.
"Now the task of the students is to keep calm and help us," he said.
Bedecked with medal ribbons on his green uniform, the mild-looking and spectacle-wearing officer was appointed to the military's top job as chief of army staff earlier this year.