The British Council cultural organisation said it had suspended its operations in the Iranian capital Tehran following cases of "intimidation" of its local staff in the country.
"Given the importance we all attach to ensuring the safety and well-being of our staff, we have had no choice but to suspend all cultural relations activities until such a time that operations can be resumed with our colleagues able to conduct their work without fear of intimidation or harassment," Deputy Director of Operations Rob Lynes said in a statement.
While officially an independent non-profit charity, the British Council receives a large part of its funding from Britain's Foreign Office.
The council, which promotes cultural and educational links, first set up an office in Iran in 1942, but closed in 1979 after the Islamic revolution. It reopened in 2001 at the request of the Iranian authorities.
The suspension came into effect on January 31, the council said, adding that it hoped to reach a deal with the Iranian authorities "as soon as possible" to resume operations.