LONDON (Reuters) - Iran said on Monday it had sentenced an Iranian woman to 10 years prison for spying for Britain, as tension rises between Tehran and some Western countries over its nuclear and missile programs.

“An Iranian who was in charge of Iran desk in the British Council and was cooperating with Britain’s intelligence agency... was sentenced to 10 years in prison after clear confessions,” Gholamhossein Esmaili, a judiciary spokesman, said on the state television.

Esmaili said the woman was in charge of projects for “cultural infiltration” in Iran. He did not identify her, but said she was a student in Britain before being recruited by the British Council.

Esmaili said the woman had been in custody for almost a year. He did not specify whether she held British nationality.

The British Foreign Office did not immediately respond to an email requesting comment. The British Council is Britain’s cultural agency overseas.

The arrest of Iranians accused of espionage has increased since Supreme Leader Ayatollah Ali Khamenei said last year there had been “infiltration” of Western agents in the country.

Iran has been increasingly at odds with Western countries since the United States withdrew from a deal Tehran signed with global powers to curb its nuclear program in return for the lifting of sanctions.

Britain is a signatory to the nuclear deal. Like other European signatories, it supports maintaining the deal.

The United States has ratcheted up sanctions against Iran this month, revoking waivers that had permitted some countries to continue buying Iranian oil. Tehran has responded by reducing curbs on its nuclear program, although steps it has taken so far stop short of violating the agreement.