At least nine people were killed in Bangladesh when opposition activists attacked a packed bus and a truck in the latest round of violence, according to local authorities.

Six of the victims, including two children, died after opposition activists hurled petrol bombs at a packed bus to Dhaka in the northern district of Gaibandha on Friday night, police official Raziur Rahman said. At least 30 people were injured, several critically, he added.

In a similar arson attack on a truck, three people died in the southern district of Barisal early on Saturday, police said.

Bangladeshi politics has been mired for years in a bitter rivalry between Prime Minister Sheikha Hasina and opposition Bangladesh Nationalist Party (BNP) leader Begum Khaleda Zia.

Both women are related to former national leaders, and they have alternated as prime minister for most of the past two decades.

The BNP refused to take part in a general election one year ago, saying it would be rigged, and intensified protests last month in a bid to force Hasina to step down and hold a new poll.

At least 70 people have been killed and hundreds injured in violence over the past month, including the latest deaths in arson attacks overnight, reports Reuters news agency.

The BNP has been blockading roads, railways and waterways and says it will continue until the government quits. It called for another 72-hour countrywide general strike from Sunday morning.

In a statement issued before news of the latest bus attack, the United States voiced grave concern over the violence and said "there is simply no justification for such actions in a democratic Bangladesh".

"We deplore the unconscionable attacks including bus burnings, throwing incendiary devices, and train derailments that have killed and wounded innocent victims," US Deputy State Department spokeswoman Marie Harf said in a statement.

Rights group Human Rights Watch also said in a statement released on Saturday that all parties should cooperate to end the cycle of violence.

Source: Reuters