Iranian chess player Sarasadat Khademalsharieh was not representing the country when she competed at international competitions in Kazakhstan without a hijab, the head of Iran's chess federation has said.
Hassan Tamini said "this chess player participated freely and at her own expense" without going through the federation, the semi-official Fars news agency reported.
"We didn't expect this chess player to do this because she had participated in the previous tournaments in compliance with the standards," he said.
Khademalsharieh, 25, took part at the International Chess Federation World Rapid and Blitz Chess Championships in Almaty.
Attendees at the event said Khademalsharieh appeared for the second day of the event, and was not wearing a headscarf.
Reports suggest that she will not return home at the end of the tournament, and will instead take up residence in Spain with her husband and child, according to the El País newspaper.
She is ranked No 804 in the world, the International Chess Federation website shows.
The woman grandmaster's profile picture on the federation's website shows her wearing a dark blue headscarf that does not cover all of her hair.
Mass protests in Iran are in their third month after the death of Kurdish-Iranian woman Mahsa Amini, 22, in police custody.
She was arrested by the morality police for being breaching the country's dress code.
Women participating in international competitions on behalf of Iran are required to wear a headscarf and abide by the dress code.
Last month, Iran denounced speed skater Niloufar Mardani after she attended a competition in Turkey without a headscarf.
Mardani participated without authorisation, Iran's Sports Ministry was quoted as saying by the Fars news agency.
In October, climber Elnaz Rekabi wore only a headband at the Asian Championships in Seoul.
She apologised for the incident and told state media that her headscarf slipped off accidentally.
Two months later, it was reported that Iranian authorities demolished Rekabi's family home for its “unauthorised construction and use of land”.
Support from footballers and athletes
Sport has become a sensitive arena during the protests, with several prominent female athletes and male footballers expressing their support.
In 2020, an Iranian chess referee said she was afraid to return home after adjudicating a women's tournament without wearing a headscarf.
Shohreh Bayat, 34, said she would not go back to Iran unless she was given security guarantees in writing from the country's chess federation.
"I really hope they will provide me something to ensure I will be safe if I come back to Iran," she said at the time.
"But if that doesn't happen, I'm just examining my options and considering anything."
Her Twitter profile says she lives in London and includes an image of her without a headscarf. She has described herself as a refugee and "human rights advocate".