Tens of thousands of people gathered in the Bangladeshi capital of Dhaka to demand the government step down and hold elections, police said.
In what is being seen as the biggest opposition demonstration since the Bangladesh Nationalist Party (BNP) suffered a landslide defeat in 2008 polls, the protest on Monday was largely peaceful but under the watchful eye of thousands of armed troops across the city.
The main opposition BNP and its Islamist ally, Jamaat-e-Islami, are demanding the restoration of a constitutional provision that required incumbent governments to transfer power to a neutral caretaker administration to conduct polls.
Prime Minister Sheikh Hasina's government scrapped the 15-year-old system last year.
The opposition, led by former Prime Minister Khaleda Zia, has said elections due in 2014 will be rigged if held under the current government without a caretaker system in place.
Al Jazeera's Nicholas Haque, reporting from Dhaka, said authorities tried to discourage opposition supporters to attend the march through a series of security measures.
"Local media are reporting that police at district level were ordered to arrest any opposition activists headed towards the capital ... [and] hundreds of people have been arrested.
"Bus, ferry, train services have also been disrupted, and so it has been very difficult for commuters to head towards the capital, even if they were just going in to work.
"Despite all of these measures, crowds have been gathering and they are here to listen to the speeches of their leader," our correspondent said.
Zia said her alliance will stage a nationwide general strike on March 29 and will escalate its protests if the system is not restored by June 11.
"We will announce a series of protests across the country if the government fails to accept our demand,'' Zia told the cheering crowd.
General strikes are a common opposition tactic in Bangladesh to highlight demands and embarrass the government.
Bangladesh, a fledging democracy, has a history of political unrest.
Zia and her archrival Hasina have alternated as prime minister since the country's last military ruler, Hussain Mohammad Ershad, was ousted in 1990.