Bangladesh's army chief vowed to back the country's interim government "come what may" to help it complete key reforms after the ouster of Prime Minister Sheikh Hasina, so that elections could be held within the next 18 months.

General Waker-uz-Zaman and his troops stood aside in early August amid raging student-led protests against Hasina, sealing the fate of the veteran politician who resigned after 15 years in power and fled to neighbouring India.

In a rare media interview, Zaman told Reuters at his office in the capital Dhaka on Monday that the interim administration led by Nobel laureate Muhammad Yunus had his full support and outlined a pathway to rid the military of political influence.

"I will stand beside him. Come what may. So that he can accomplish his mission," Zaman, bespectacled and dressed in military fatigues, said of Yunus.

The pioneer of the global microcredit movement, Yunus has promised to carry out essential reforms to the judiciary, police and financial institutions, paving the way to hold a free and fair election in the country of 170 million people.

Following the reforms, Zaman - who took over as the army chief only weeks before Hasina's ouster - said a transition to democracy should be made between a year and a year-and-a-half, but underlined the need for patience.

"If you ask me, then I will say that should be the time frame by which we should enter into a democratic process," he said.

Bangladesh's main two political parties, Hasina's Awami League and its bitter rival Bangladesh Nationalist Party, had both previously called for elections to be held within three months of the interim government taking office in August.

Yunus, the interim administration's chief adviser, and the army chief meet every week and have "very good relations", with the military supporting the government's efforts to stabilise the country after a period of turmoil, said Zaman.

"I'm sure that if we work together, there is no reason why we should fail," he said.

More than 1,000 people were killed in violent clashes that began as a movement against public sector job quotas in July but escalated into a wider anti-government uprising - the bloodiest period in the country's independent history.