
Activists belonging to the Jamaat-e-Islami party, many carrying sticks and throwing rocks, fought running battles with steel-helmeted riot police in Dhaka and set at least 30 vehicles on fire.
Twenty people were wounded and police detained nearly 25, the witnesses said.
"The violence has spread through a large part of the city, with smoke from the burning vehicles filling the sky," a witness said.
There were similar clashes in Chittagong, Comilla and other cities in which 50 people including police were injured.
Police said Jamaat called the marches to demand the release of the party's top leaders who have been held in prison for months, facing charges of acts of genocide during Bangladesh's 1971 war of independence against Pakistan.
Jamaat, a political ally of the main opposition Bangladesh Nationalist Party (BNP) led by former prime minister Begum Khaleda Zia, has vowed to free their leaders and support BNP's campaign to oust the government of Prime Minister Sheikh Hasina from power.
The government has rejected BNP's demand for early elections, saying there will be no vote before Hasina completes her five-year term at the end of 2013.
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