Opposition supporters set fire to six buses on the eve on Saturday of a general strike protesting government moves to amend the constitution, in Bangladesh's second nationwide shutdown this month, police said.
No one was hurt in the attacks on the buses, which were parked in central Dhaka awaiting passengers, police officer Krishnapada Roy said.
Roy said security has been tightened to prevent violence during the strike.
The main opposition Bangladesh Nationalist Party and its Islamic fundamentalist ally, Jamaat-e-Islami, said they will enforce a 36-hour strike beginning at dawn Sunday.
The opposition staged a similar shutdown early this month.
It says the government wants to repeal a constitutional provision that requires it to hand over power at the end of its term to a nonpartisan administration to conduct new polls. A former chief justice is usually chosen to head the three-month caretaker administration.
The change would mean the next general elections due in 2014 would be overseen by Prime Minister Sheikh Hasina. That could lead to vote-rigging favoring Hasina's party, opposition spokesman Mirza Fakhrul Islam Alamgir said on Saturday.
"The government wants to cling to power. That's why it wants to amend the constitution," Alamgir said.
The government denies the charge.
The move came after the Supreme Court ruled that the provision, included in the constitution in 1996, is undemocratic.
Since the provision's introduction, Bangladesh has held three parliamentary polls supervised by nonpartisan interim governments.
In a speech Friday, Hasina urged the opposition to discuss the issue in Parliament.
"Politics should be discussed in Parliament, not in the street," Hasina said.
In Bangladesh, opposition groups commonly enforce general strikes to highlight their demands.