 Security has been tightened in the capital, Dhaka |
The blockade of roads, railways and ports is being organised by an alliance of political parties who want elections scheduled for this month postponed.
The Awami League and its allies say they will boycott the 22 January poll, alleging it will not be free and fair.
But Bangladeshi President Iajuddin Ahmed says the elections will go ahead.
The BBC's John Sudworth in the capital, Dhaka, says this is a constitutional crisis being played out on the streets.
He says the army is patrolling Dhaka, a clear sign of the threat of a repeat of the scenes of violence that have marred the previous protests over the past few months.
Our correspondent says police have already baton charged some protesters in the capital, where the situation is very tense.
Previous agitation over the issue has led to more than 30 deaths countrywide.
'Arrests'
Opposition spokesman Abdul Jalil said: "We will not accept farcical elections. We will shut down the country for weeks if the government goes ahead with holding the elections."
But President Ahmed, head of the caretaker government, said the constitution demanded the polls be held within 90 days, and they would proceed.
The Bangladesh Nationalist Party (BNP)-led government handed power to the interim administration at the end of October.
The Awami League said more than 1,000 activists were detained ahead of the protests.
Its main demand is that the government use an updated version of the 2000 voter register, and not one created over the past few years.
The political bloc led by the BNP accuses the Awami League of "sensing defeat" and being determined to sabotage the elections.
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