There was heavy security on the streets but no immediate signs of violence, witnesses said.
Hundreds of activists of the multi-party alliance led by former prime minister Sheikh Hasina, head of the Awami League, gathered in Dhaka despite an indefinite ban on rallies and demonstrations in the capital.
Authorities deployed nearly 15,000 police, elite forces and paramilitary troops to maintain law and order in the city, home to 10 million people.
Few buses moved early this morning with very few passengers, witnesses said. Schools were shut.
Correspondents in the southern port city of Chittagong, the northeastern city of Sylhet and Khulna in the southwest said the blockade had also taken effect there and in nearby towns.
''We have instructed our followers to paralyse the country .. including ports, buses, trains and ferries,'' Awami general secretary Abdul Jalil told reporters.
The home ministry said late on Friday that anyone trying to create violence would be dealt with severely.
The blockade follows expiry of a deadline Hasina had set the interim government to remove Chief Election Commissioner M A Aziz and his deputies for their alleged bias towards the Bangladesh Nationalist Party (BNP) of Begum Khaleda Zia, whose term as prime minister ended last month.
The BNP denies the allegation, accusing the Awami League of trying to push the country into anarchy and sabotage the polls.
''They are working on a sinister design to halt the process of the election in January,'' BNP secretary-general Abdul Mannan Bhuiyan said late yesterday.
Visiting U S Assistant Secretary of State Richard Boucher said yesterday: ''Violence does not do any good. Political parties should work with consensus to lower the level of violence as you proceed to elections''.
He added: ''The United States hopes to see a free, fair and non-violent election in Bangladesh. The caretaker government has a big task ahead ... the election commission needs to be free of influence.'' Bangladesh elections in the past have been marred by violence and allegations of rigging and voter intimidation.
At least 30 people were killed and hundreds injured in clashes between rival political activists in late October.
REUTERS SP RN0844