However, the 20-Party Alliance that it leads has not announced fresh demonstrations.
The coalition enforced a daylong shutdown on Monday across Bangladesh.
"Government agents killed school teacher Shamsunnahar [Jhorna]," BNP's acting Secretary General Mirza Fakhrul Islam Alamgir further claimed.
He condemned the killing and demanded arrest of the perpetrators.
"They (the government) torched vehicles and went on the rampage before the shutdown as they had done before," he alleged.
Such incidents had taken place before the Jan 5 polls, he said.
He attributed Monday's train-lorry collision near Kamalapur, killing six people, to government mismanagement.
He claimed over 300 of their activists had been arrested during the shutdown while another 110 were injured in police attack
Police had cordoned off the party headquarters since morning.
Asked about fresh agitation plans, Fakhrul said, "We'll announce them in time."
He claimed the people had "spontaneously" observed the strike.
"The government sabotaged opposition party's programmes and attacked the people.
"It is now trying to blame the opposition for their violence.
"The aim is simple, to divert the people's attention from our movements," the BNP leader alleged.