More than 120 schoolgirls and three teachers have been poisoned in the second attack in as many months in Afghanistan blamed on conservative radicals in the country's north, Afghan police and education officials have said. 

The attack occurred on Wednesday in Takhar province where police said the Taliban, who are opposed to education of women and girls, had used an unidentified toxic powder to contaminate the air in classrooms, leaving scores of students unconscious.

Afghanistan's intelligence agency, the National Directorate of Security (NDS), said the Taliban appear intent on closing schools ahead of a 2014 withdrawal by foreign combat troops.

From the perspective of one neighbourhood in Herat

"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," NDS spokesman Lutfullah Mashal said.

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

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

Since 2001, when the Taliban were toppled from power by US-backed Afghan forces, three million school-aged girls have returned to school. 

Women were previously banned from work and education under Taliban rule.

There are still periodic attacks against students, teachers and school buildings, usually in the more conservative south and east of the country, where the Taliban draws most of its support