Over 4,000 activists of eight Islamist parties were sued in connection with Sunday's violence that killed four people and injured 50 in Manikganj.
The violence erupted when police, having been attacked by pickets, opened fire in Singair upazila of the district during countrywide hartal called by the Islamist parties.
A total of six cases were filed with Singair Police Station on Sunday night on charges of killing, arson, vandalism and attacking police, police sources said.
Raiding different parts of the district on that night, police detained 13 people for their alleged involvement in the violence, said Md Mizanur Rahman, additional superintendent of police of Manikganj.
Police sued 4,553 supporters, mentioning names of 20, of Khelafat Majlish and seven other Islamist parties, he said.
A one-member probe body, headed by the additional SP, has been formed to investigate two of the six cases.
Foyjur Rahman, son of Abdul Majed Khan, filed a case against 20 named and 100 unnamed people on charge of attacking his father during the clash, the additional SP said.
Majed is the general secretary of Singair upazila unit Awami League.
Businessmen Azhar and Abdul Quader filed two separate cases against 355 people in connection with vandalising their business establishments at Kashimpur Bazar.
Reajul Islam, of Joymantap village in the upazila, filed a case against 33 named and 25 unnamed persons, the additional SP said.
Reajul was injured during a clash between supporters of Islamist parties and police on Sunday, he added.
Meanwhile, eight Islamist parties observed a daylong hartal in the district yesterday, protesting the killing of their "activists" during Sunday's violence.