Violent protests have erupted across Bangladesh, a day after nearly 20 people were killed and more than a hundred wounded in grenade attacks on an opposition rally. Security has been tightened across the country.

Angry mobs set fire to a train midway through its journey from the port city of Chittagong to the capital, Dhaka, after forcing some 600 passengers off the train. Riot police fired tear gas to disperse the protesters.

Opposition party supporters also ransacked a railway station near Chittagong. In several other towns, officials reported clashes between police and protesters.

Angry party workers have taken to the streets since Saturday evening, when several grenades were hurled at a packed opposition rally being addressed by former Prime Minister Sheikh Hasina Wajed. She escaped unhurt, but many people were killed or wounded.

General-secretary of the opposition Awami League party, Abdul Jalil says the protests will continue. "Our demand is the government should resign immediately. They should quit," he said.

Prime Minister Khaleda Zia has strongly condemned Saturday's attack on the opposition rally, and promised an investigation.

Paramilitary troops have been deployed in Dhaka, where tension is running high. Traffic was thin on Sunday, as many people stayed off the roads, fearing violence.

The Awami League has called for a two-day nationwide protest strike starting Tuesday. Party General-Secretary Jalil describes Saturday's attack as an assassination attempt on the party's leader, Sheikh Hasina.

"Last evening's attack was to kill Sheikh Hasina, because she has been carrying the mantle of secular, democratic forces in Bangladesh," he said.

No one has claimed responsibility for the explosions that targeted the rally. The attack was the latest in a series of blasts in Bangladesh this year.