The UN children's agency says the Afghan economy has lost an estimated 500 million dollars because of limited access to education by girls in Afghanistan over the past year.

The Taliban have not allowed secondary schools for girls to reopen since it retook power on August 15 last year under the group's own interpretation of the Islamic law.

UNICEF released the report on Monday, exactly one year after the Islamist group took over control of the country.

It says keeping girls out of secondary school cost Afghanistan 500 million dollars, or 2.5 percent of its gross domestic product for 2020.

The report also says if the 3 million girls currently out of school were able to complete their secondary education and participate in the job market, girls and women would contribute at least 5.4 billion dollars to the Afghan economy during their lifetimes.

The report also touches on the negative impacts of girls not being able to return to secondary school in areas other than economy. It says UNICEF is struggling to reach girls to give nutritional support and hygiene information that it used to provide at schools.

A UNICEF official calls for girls' immediate return to schools, saying education is not only a right of all children, but the backbone for Afghanistan's future growth.