Attackers in Bangladesh threw crude fire bombs at a packed bus and a moving truck in two separate incidents, killing at least nine people and injuring 30 others, police said Saturday.

The attacks were the latest spasm of violence in a nationwide transportation blockade called by the opposition to pressure Prime Minister Sheikh Hasina to resign and announce new elections. The violence brought the death toll to 63 since the blockade started Jan. 6.

Former Prime Minister Khaleda Zia, chief of the opposition Bangladesh Nationalist Party, has vowed to continue the blockade to unseat the government despite the deaths and calls from business leaders and Western diplomats to stop the action.

The bus was attacked late Friday night in northern Gaibandha district while it was traveling toward the capital, Dhaka, amid a police escort, said local police official Raziur Rahman. At least six people were killed and 30 injured in that incident.

Rahman said the perpetrators fled into the darkness and their identities were not known.

The injured were being treated for severe burns and the death toll could rise, said Abdul Kader Khan, a deputy director at Rangpur Medical College and Hospital.

In the other incident, a truck carrying poultry was attacked before dawn Saturday in southern Barisal district, killing the driver and two other people, said local police official Sajjad Hossain.

The opposition has announced a 72-hour nationwide general strike beginning Sunday demanding that schools, offices and businesses stay closed.

Prime Minister Hasina has refused to sit down with the opposition, blaming it for the attacks, while Zia says the government is behind the violence.

Zia's party and its partners boycotted 2014 elections after Hasina refused to appoint a neutral government to monitor the voting. That allowed Hasina to return to power for five years. Hasina says new elections will not be held before 2019.

The renewed violence ended a year of relative calm in Bangladesh, where politics has long been accompanied by chaos. Political violence left nearly 300 people dead in 2013.