Golam Mostofa, 29, a businessman, filed the case with Dhaka Metropolitan Magistrate Court accusing the SP and 15 others.
Court Judge Didar Hossain directed the Police Bureau of Investigation (PBI) to investigate the matter and submit a report within November 1.
According to the case statement, on August 8, a group of 15-16 people identifying themselves as 'DB men', led by Belayet Hossain, went to the victim's house and demanded Tk 25 lakh.
They threatened to implicate the victim in an arms case and fine his business establishment in Narayanganj through mobile courts if the money is not paid.
The DB men blindfolded him and beat him up mercilessly, he added.
The SP beat up the victim and took him to the DB office on Mintu Road where he again threatened to kill Mostofa in crossfire and implicate him in a drug case if the money is not given.
Mostafa instantly paid Tk 3.5 lakh and gave Tk 50,000 more on August 10.
Later, Mostafa’s father settled the matter with the SP promising him to pay total Tk 15 lakh while he also paid a cheque of Tk 5 lakh. The SP demanded Tk 6 lakh more within seven days.
Two years back, Mostafa got acquainted with Belayet and friendly relationship developed between them.
Belayet took a loan of Tk 5 lakh from the victim’s father on August 11, 2019 which he paid back through a check on March 15.
On April 4 this year, Belayet called the victim's father over cell phone demanding Tk 5 lakh and threatened him.
On April 10, Mostafa came to know from his father that Belayet had taken the money through fraudulence.