Dhaka: Unidentified arsonists set fire to at least five primary schools, including four polling booths, in Bangladesh, police said on Saturday, the eve of a general election that the main opposition party is boycotting.

Police are investigating the fires in Gazipur, on the outskirts of capital Dhaka, but suspected that wrongdoers aiming to disrupt Sunday's election had set fire to the schools in the middle of the night.

"We have intensified patrolling and remain on high alert to thwart any untoward incident," said Gazipur police chief Kazi Shafiqul Alam.

The main opposition Bangladesh Nationalist Party (BNP), boycotting for the second time in three elections, says Prime Minister Sheikh Hasina's Awami League is trying to legitimise a sham vote that will deliver her party a fourth straight term.

Hasina, refusing BNP demands to resign and cede power to a neutral authority to run the election, accuses the opposition party of instigating anti-government protests that have rocked Dhaka since late October and killed at least 10 people in the South Asian country.

The BNP has asked citizens to shun the poll and called a two-day strike in the country from Saturday.

Roads in Dhaka, clogged with traffic on normal days, were largely deserted on Saturday, with security forces patrolling the city in armoured vehicles.

Arsonists attacked polling booths in the northeastern districts of Moulavibazar and Habiganj, police said, adding that similar incidents had been reported across the country over the past two days.

In the coastal district of Khulna, police arrested two people on Thursday night after local citizens caught them allegedly trying to set fire to a school.

Another attempt to set fire to a primary school building in the same area was averted by locals on Friday, said Saidur Rahman, Khulna's police chief.

"We are on alert and are on the lookout for the arsonists," Rahman said.

About 800,000 police, paramilitary and police auxiliaries are to guard polling booths on Sunday. Officials of the army, navy and air force have also been deployed across the country to maintain peace.

In a separate incident on Friday night at least four people, including a child, died in a suspected arson attack on a passenger train, police said.

In addition to the deaths, eight were injured when fire spread to four compartments of the Dhaka-bound Benapole Express around 9 p.m. (1500 GMT) on Friday.

Last month protesters set a train ablaze, killing four people during a countrywide strike called by the opposition.

Senior BNP official Ruhul Kabir Rizvi said Friday's incident on the Benapole Express was "undoubtedly an act of sabotage and cruelty against humanity", blaming the ruling party for it.

The Awami League party accused the BNP of trying to disrupt the election by creating a "reign of terror on innocent people".

The train fire in Dhaka's Wari area was brought under control by seven firefighting units after about an hour, fire service official Shahjahan Sikder said.