An angry mob set fire to a passenger train in central Bangladesh Sunday, injuring at least 20 people, in retaliation for a grenade attack on an opposition rally that killed 18 people and wounded hundreds, police said. The train was traveling to the capital, Dhaka, from southeastern Chittagong city, police said. Riot police fired tear gas shells to disperse the protesters near Bhairab town, 80 kilometers (50 miles) east of Dhaka, said Fazlul Huq, chief traffic controller of state-run Bangladesh Railways. Police said at least 20 people were wounded in the train attack. On Saturday, the country's main opposition leader, Sheikh Hasina, escaped injury when about a dozen bombs exploded as she addressed supporters outside her Awami League party's headquarters in Dhaka. In that attack, at least 18 people were killed and more than 300 injured, including senior opposition members, ATN Bangla TV station reported Sunday. The toll increased after four more deaths were reported in area hospitals, it said. In the capital, police recovered two unexploded bombs from inside Dhaka Central Jail and at a market outside it, an official said on condition of anonymity. Traffic was light on the city's streets as many schools and shops were closed for fear of more violence.