A murder investigation has been opened into Bangladesh's ex-premier Sheikh Hasina over the police killing of a man during civil unrest.

Six other top figures in the previous government are also being investigated following weeks of deadly unrest in the capital Dhaka.

Mamun Mia, a lawyer who brought the case on behalf of a private citizen, said the court in Dhaka had ordered police to accept "the murder case against the accused persons".

This is the first step in a criminal investigation under Bangladeshi law.

Ms Hasina resigned and fled the country earlier this month, fleeing to neighbouring India, as calls grew for her to stand down.

More than 400 people were killed in weeks of student demonstrations culminated in the demands against Ms Hasina. Many of them were shot by the police, on her orders.

Businessman Amir Hamza applied to bring the murder case in July, after a local grocer Abu Saeed was shot in the head while crossing the road.

He told a court that on 19 July, students were holding a peaceful protest, alleging police had fired indiscriminately on the crowd, according to BBC Bangla.

Mr Hamza said he was not related to Mr Saeed but approached the court because the grocer's family did not have the finances to file the case.

"I am the first ordinary citizen who showed the courage to take this legal step against Sheikh Hasina for her crimes. I will see the case to an end," he told Reuters news agency.

Magistrate Rajesh Chowdhury ordered the police to investigate the case, the first to be brought against Ms Hasina since the protests started.

The former Transport and Bridges Minister Obaidul Quader is among those being investigated.

Ms Hasina's government, which was in power for 15 years, was accused of widespread human rights violations and dogged by allegations of rampant corruption.

The student protests began in early July, starting out as peaceful demands to scrap quotas in civil service jobs, before transforming into a wider movement which toppled the government.

Ms Hasina urged police to clamp down hard on the protestors, referring to them as "not students but terrorists who are out to destabilise the nation".

The recently formed new government contains many of the protestors, and is helmed by Nobel Peace laureate Muhammad Yunus.

Ms Hasina will return to the country when elections are declared, her son Sajeeb Wazed Joy has said.