Dhaka, Bangladesh ? A series of bombs exploded as a top Bangladeshi opposition leader was speaking at a rally from atop a truck Saturday, killing at least 14 people and injuring hundreds, witnesses and news reports said.

The main opposition leader, Sheikh Hasina, crouched low in the truck soon after the first blast occurred as she was addressing thousands outside her Awami League party’s headquarters in central Dhaka. She was visibly shaken but not hurt.

At least 14 people were killed and more than 300 injured, including senior opposition members, United News of Bangladesh reported. Doctors at Dhaka’s state-run hospital were overwhelmed and appealed for blood, saying the death toll could increase because some of the injured were in critical condition.

No one claimed responsibility for the blasts, but Awami League General Secretary Abdul Jalil claimed they targeted Hasina. The rally was called to protest a series of explosions early this month that killed two people, including an opposition supporter, in the northeastern city of Sylhet.

Police gave few details, but Hasina aide Saber Hossain Chowdhury said the first blast was followed by at least eight other explosions and numerous gunshots, and the jeep that carried Hasina away had several bullet marks in the rear glass.

“It seemed to me that some of the bombs were thrown from multistory buildings near the scene,” said Farook Khan, an opposition lawmaker who was standing close to Hasina.

Khan estimated that at least 15,000 people were at the rally when the explosions happened.

Prime Minister Khaleda Zia condemned the “dastardly attack on a political rally” and said her government would try to find those responsible.

“Let us all work together to prevent repeat of such cowardly attacks,” she said in a statement.

Angry opposition supporters smashed or burned dozens of passing vehicles to protest the attack. Police fired tear gas to disperse the rampaging crowd, witnesses said, while security forces patrolled the streets.

Violence also spread to about a dozen other cities and towns, where protesters smashed vehicles and attacked shops, witnesses said. Security was stepped up across the country, authorities said.

Hundreds of Bangladeshis thronged outside the hospital looking for their loved ones. Many of the injured arrived at hospitals in slow-moving rickshaws.

Bangladesh, an impoverished nation of 140 million people, has a history of political unrest.

It has witnessed two presidents assassinated in military coups and 19 failed coup attempts since gaining independence from Pakistan in 1971.