DHAKA, Bangladesh (AP) — Bangladesh’s railway minister accused the country’s main opposition party of “arson” and “sabotage” after a fire broke out early Tuesday on a passenger train in the capital, killing four people including a mother and child.

Nurul Islam Sujon accused the Bangladesh Nationalist Party, led by former Prime Minister Khaleda Zia, of resorting to violence in the name of anti-government protests to thwart the January 7 national election and “create chaos.”

Zia’s party — which is boycotting the election — issued a statement denying the accusation.

“There is deep suspicion among the public whether this incident has been carried out as a ploy to divert public attention from the ongoing democratic movement,” said the party’s Senior Joint Secretary General Ruhul Kabir Rizvi.

The party has been intermittently enforcing transportation blockades and general strikes demanding the resignation of Prime Minister Sheikh Hasina, who seeks to return to power for a fourth consecutive term.

Firefighters on Tuesday recovered four bodies after three coaches of the Mohanganj Express train caught fire, said Shahjahan Sikder, deputy assistant director of the Bangladesh Fire Service and Civil Defense. The train had left the northern district of Netrokona late Monday for Dhaka and was packed with passengers.

A 32-year-old mother and her 3-year-old son were among the dead, said Sikder.

It wasn’t clear what caused the fire and police were investigating.

Zia’s party called for a daylong general strike on Tuesday across the South Asian nation as part of their anti-government movement ahead of elections. On Monday, about 1,900 candidates, including many independents, started campaigning in the 300 constituencies. Hasina, the current premier and head of the ruling Awami League party, is set to begin her campaign from the northeastern city of Sylhet on Wednesday.

Zia’s party has called for a boycott of the polls after its demands for a caretaker government to oversee the election were not met. The party accused Hasina of rigging the 2018 vote and said it does not have any faith the coming election would be fair.

The boycott means voters have little choice but to reelect Hasina. The election takes place as the government has cracked down on opposition politicians. Zia’s party said more than 20,000 party people have been arrested since October 28, when a police official was brutally killed during a massive rally, allegedly by Zia’s supporters.

The government has denied accusations of targeting the opposition but warned that any “acts of sabotage” or “attempts to create chaos” in the country would not be tolerated. Hasina has pledged a free and fair election, and encouraged independents to contest it.