The attack coincided with the nationwide stoppage called by the main opposition Bangladesh Nationalist Party (BNP) on Tuesday as part of its ongoing campaign to boycott the polls and launch a formal protest against the Election Commission's polls schedule.

The arson attack on the train was the fifth in the past month but the deadliest so far in terms of casualties.

The miscreants set on fire three compartments of the Dhaka-bound inter-district Mohanganj Express early morning shortly after the train left the Airport Railway Station at the entry point of the capital, police and witnesses said.

“The passengers saw the fire after the train left the Airport station, it was stopped at the next stop at Tejgaon station,” Tejgaon police station officer-in-charge Mohammad Mohsin said.

At least four persons, including a woman and her child, have died after the train was set on fire amid a hartal called by the BNP.

Mohsin said another minor boy was missing while his mother awaited in front of the gutted compartment as fire service rescuers were searching inside.

Railway officials said the locomotive master halted the train at Tejgaon where the fire service rescuers doused the blaze and retrieved four bodies while two of the dead remained unidentified.

Prime Minister Sheikh Hasina’s ruling Awami League has emerged as the prime contender in the absence of ailing ex-premier Khaleda Zia’s BNP which has boycotted the January 7 polls since its demands for a no-party caretaker government to organise the voting were not met.

Awami League is contesting the polls against its technical Opposition in Parliament Jatiya Party and independent candidates, including the rebel contenders who fielded their candidature after failing to secure the party nomination.

Awami League earlier said it would encourage the independent, including the party’s rebel candidates to make the polls participatory though voters have little option other than reelecting the ruling party for the fourth consecutive term since the December 2008 elections.

One passenger was killed last week and dozens wounded as saboteurs uprooted railway tracks on the same train on the same route last week when seven carriages derailed in Gazipur on the outskirts of the capital.

Dozens of trucks, buses and private cars were torched since late October while the violence killed at least six persons.

Hasina, meanwhile, said, "They can't oust the government by killing people”.

Bangladesh will deploy the Army for 13 days from December 29 to maintain order “in aid of civil power” ahead of the January 7 general elections amid the political unrest. However, the military called it a routine poll time duty.

The Election Commission announced the polls schedule on November 15 amid continued political unrest.

BNP has repeatedly been saying no election under the ruling Awami League would be fair, demanding the government’s resignation to pave the way for an interim non-party neutral government for polls oversight.

Chief Election Commissioner Kazi Habibul Awal earlier said despite the need for a “congenial atmosphere” for a smooth election, “for a long time there exist differences of opinions among political leaderships on the question of election, particularly over the institutional method of the polling”.

In a veiled reference to BNP and its allies, Awal said his office invited all registered political parties who were “reluctant” to take part in the upcoming polls for dialogues with the Commission but “they rejected the invitation”.

But he asked the nearly 110 million voters to freely exercise their rights franchise in an “enthusiastic atmosphere, discarding all worries, tensions and unease”.

BNP had boycotted the 2014 election but took part in 2018 polls, which party leaders later said was a mistake alleging that the voting was marred with widespread rigging and intimidation.

According to media reports, over 10,000 opposition leaders and activists, including BNP Secretary General Mirza Fakhrul Islam Alamgir have been arrested in a nationwide crackdown while BNP claimed the figure to be as high as 20,000.

A Dhaka court on Monday denied a bail request from Alamgir, meaning he could not guide his party ahead of the election next month.

He is the key party leader since the ailing Zia is hospitalised and faces 17 years of imprisonment following her conviction in two corruption cases that her party says were politically motivated.