More than 100 people including many police were injured in clashes Sunday between opposition activists and security officials in southeastern Bangladesh, witnesses said.
The United News of Bangladesh news agency said the violence broke out in Chittagong when police blocked a protest march by Jamaat-e-Islami, the country's largest Islamic party. It said police swung batons and fired tear gas to disperse the stone-throwing protesters.
Witnesses said at least 100 people were injured.
Local journalist Osman Gani Mansur said the protesters smashed at least 50 vehicles and set fire to at least three others in Chittagong, Bangladesh's second-largest city, 215 kilometers (135 miles) southeast of Dhaka.
Amir Khasru Mahmud Chowdhury, an opposition spokesman, said dozens of protesters were arrested.
The main opposition Bangladesh Nationalist Party and its 17 allies including Jamaat-e-Islami held rallies across the country Sunday to protest the disappearance of one of its leaders.
The opposition blames the government and security agencies for the disappearance of Elias Ali on April 17 but authorities deny the allegation.
The opposition alliance staged nationwide general strikes for five days last month to demand that the government find Ali. It also is insisting that the government of Prime Minister Sheikh Hasina restore a system of caretaker governments to oversee general elections, which are next due in 2014. The government scrapped the 15-year-old system last year, and the opposition accuses it of planning to rig the elections.
Amnesty International and New York-based Human Rights Watch have expressed concern over recent disappearances in the country and urged Bangladesh to investigate them.
At least 22 people have disappeared this year, according to the local rights group Ain-o-Salish Kendra. Another group, Odhikar, says more than 50 people have disappeared since 2010. Many of those missing are politicians.