More than 120 schoolgirls and three of their teachers have been poisoned for a second time in as many months in northern Takhar province.

Police say Wednesday's poisoning occurred after an unidentified toxic powder was introducted into the air in the classrooms.

The National Directorate of Security (NDS), the Afghan intelligence service, says the posionings are part of the Taliban's spring offensive.

"A part of their Al Farooq spring offensive operation is ... to close schools. By poisoning girls they want to create fear. They try to make families not send their children to school," Lutfullah Mashal, NDS spokesman, said. 

The Ministry of Education said last week that 550 schools in 11 provinces where the Taliban have strong support had been closed.

Last month, 150 schoolgirls were poisoned in Takhar province after they drank contaminated water.