A suspected arson on a train has killed four people in Bangladesh ahead of a general election.

The fire broke out on the train as it was heading to the capital, Dhaka, and gutted multiple cars on Friday night.

Officials say two of the victims are children.

Police believe the blaze was an arson intended to sabotage Sunday's election.

Opposition parties are boycotting the election after their supporters clashed with police during protests against the government last year.

Some of the protesters turned violent and set buses on fire.

Prime Minister Sheikh Hasina has responded with heavy-handed measures, including detaining senior opposition members.

Foreign observers have been dispatched to help ensure a free and fair election. But there are fears that the security situation will deteriorate.