The Taliban have banned Afghan women from working at non-governmental organizations (NGOs) in the country.
The economy ministry says the ban applies to the Afghan coordinating body for humanitarian organizations, known as ACBAR - which does not include the United Nations.
However, the UN contracts NGOs that are part of ACBAR in Afghanistan to carry out their humanitarian work.
The letter said female employees would not be allowed to work in NGOs until further notice because some did not adhere to the Taliban's interpretation of Islamic dress codes for women.
The economy ministry explained that it had received "serious complaints" about female employees not wearing the headscarf or the "correct" headscarf.
This ban comes days after the Taliban banned Afghan women from going to university, in a move that drew international condemnation.
When they seized power last year, the Taliban promised more moderate governance of women's rights - but have since continued to enforce their interpretation of Islamic law - barring them from schools, most jobs, parks, and gyms.
Women in the country are also required to wear traditional clothing from head to toe while in public.