More than 400,000 children in Afghanistan are expected to drop out of school in 2017 due to growing instability in the country and the forced returns of Afghan refugees from Pakistan, according to rights group Save the Children.

"We know that children who aren't going to school are at increased risk of early marriage, entering the workforce where they can be exploited, or even recruitment into armed groups or being trafficked," the group's Afghanistan director Ana Locsin said in a statement Thursday.

According to the statement, more than 610,000 Afghans were forced to return from Pakistan in 2016 and up to one million more will return this year to the war-torn country.

"Over half of all returnee children are currently out of school, often working on the streets," Save the Children said.

Conflict has also forced more than 1000 schools to shut, authorities have reported in the past months.

That today millions of children are going to school in Afghanistan, including girls, has long been considered a success story of international aid efforts in Afghanistan.

Recently, however, figures have been called into question. In December, education minister Asadullah Balkhi claimed that figures previously presented by the Afghan government and international organisations were incorrect.

Instead of the claimed 11.5 million, only a little more than 6 million children were actually in school, Balkhi said.