The suspected blockaders hurled several rounds of petrol bombs on the train this afternoon near western Iswardi Railway Station on its way back to Dhaka, railway officials said.
No passenger was injured in the attack which caused minor damage to the engine as the bombs exploded under its wheels, a railway spokesman said.
The attack is the latest in a spate of political violence that has claimed 75 lives so far in Bangladesh, where the opposition BNP has clamped an indefinite countrywide blockade.
At least nine persons, including three children, were burnt alive in the past two days when opposition activists hurled petrol bombs at a packed bus and a truck.
Railway officials said this was the eighth such attack on trains in the country since former Prime Minister Khaleda Zia's BNP launched the transport blockade on highways, railways and waterways on February 6 as part of their protest against Sheikh Hasina government, demanding mid-term elections.
After the attack on 'Maitree Express', a changed engine later brought the carriages to Dhaka with passengers on board, said Sayedur Rahman, assistant director of Bangladesh Railway.
A manhunt is underway to track down the attackers.
The incident took place on the first day of a fresh 72-hour spell of general strike, that began on Sunday, sponsored by the BNP-led 20-party alliance.
The attack on Maitree Express came five days after saboteurs uprooted tracks derailing a train injuring five people and delinking southeastern port city of Chittagong with rest of the country for hours in railway routes.
"Since the unrest began, we issued directives for passengers to keep shut the windows and loco masters to keep an extra eye on tracks and limit the speed within 40 kilometres per hour instead of routine 70 km per hour this has caused a collapse schedule but so far we evaded any deadly crashes," a railway official said.