DHAKA: Bangladesh's main opposition party on Tuesday boycotted three mayoral elections over accusations of massive rigging, fanning fears of further unrest in the South Asian nation.

Political uncertainty has persisted since January 2014, when Prime Minister Sheikh Hasina's Awami League won a second consecutive term after a bloody parliamentary election boycotted by the main opposition Bangladesh Nationalist Party (BNP).

The BNP, led by Khaleda Zia, has stepped up protests this year in a bid to force Hasina to step down and hold a new vote under a neutral caretaker administration after last year's poll, which was deemed by international observers to be flawed.

Read more: Bangladesh ruling party wins polls hit by violence, boycott

Tuesday's mayoral elections are being held for two city corporation posts in Dhaka, the capital, and one in the port city of Chittagong, with a total of six million eligible voters.

The elections are supposed to be nonpartisan but both the ruling party and the opposition BNP directly backed candidates.

“This is not an election,” senior BNP leader Moudud Ahmed told reporters.

“The ruling party are voting for themselves by capturing polling centres.”

Voter turnout was barely 5pc, he said, adding, “We participated in the city polls to restore democracy. But vote rigging has already proved that restoring democracy is not possible under this government.”

Officials of the ruling party were not immediately available to respond to Ahmed's comments.

Zia and leaders of her party had earlier threatened retaliation if the local elections were rigged.

Read more: Thirty-four die in Bangladesh vote protest violence

More than 120 people have been killed and hundreds injured in political violence, most in petrol bomb attacks on vehicles, amid transport blockades and strikes by the opposition aimed at toppling the government.

Political unrest over the past three months has cost at least 0.6pc of the country's gross domestic product.

Zia, 69, won bail this month in two graft cases. She denies wrongdoing, saying the charges against her and her party are politically motivated.

She also faces charges of instigating the latest violence.

Bangladeshi politics has been mired for years in rivalry between Hasina and Zia. Both are related to former national leaders and have alternated as prime minister for most of the past two decades.

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