The Bangladesh Nationalist Party party (BNP), led by Khaleda Zia, is calling for the government to step aside ahead of the polls due in January.
The strike is going ahead despite pleas from PM Sheikh Hasina.
In comes after at least six people were killed during fresh unrest on Friday.
The violence flared as police and protesters clashed in some parts of the country, leaving more than 100 injured.
The strike began at 06:00, with the BNP and its Islamist ally the Jamaat-e-Islam hoping to bring the country to a standstill.
They want to force the prime minister to allow a neutral caretaker administration to oversee the election process.
But Sheikh Hasina, who heads the Awami League, has rejected such a plan saying there is no scope for unelected people to supervise the vote.
Khaleda Zia announced that the national shutdown would be going ahead from Sunday, despite a rare phone call with Sheikh Hasina in which the the prime minister asked her to call off the strike.
It is thought to be the first time the bitter rivals have spoken directly for a decade.
The BNP and its allies are refusing to participate in elections under current constitutional provisions, which do not allows for a neutral, caretaker government, or require the incumbent prime minister to step down during the interim period.
The opposition fears the government will rig the polls if it remains in power.
Friday’s violence came as security officials opened fire on opposition supporters trying to defy a ban on protests.
Two people were killed in the coastal district of Cox’s Bazar, according to reports.
Local media said at least two people had died in the central district of Chandpur, while protesters also died in the northern town of Jaldhaka and the northern district of Nilphamari.
Demonstrators set vehicles on fire in the capital Dhaka.
A series of rulings against Jamaat have led to violent protests across Bangladesh, with more than 150 people killed in clashes with police since the beginning of this year.
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