A British football fan has been arrested and detained in the United Arab Emirates after reportedly wearing a Qatar team shirt to a match.
Ali Issa Ahmad, 26, from Wolverhampton, is said to have been unaware of a law against "showing sympathy" for Qatar - brought in over a diplomatic dispute.
A friend says he was later accused of making false claims about officials.
The Foreign Office said it was providing assistance to a UK citizen and was in touch with UAE authorities.
The UAE and four other countries in the region are currently engaged in a political and diplomatic stand-off with Qatar after they accused the state of supporting radical and Islamist groups.
On its website, the Foreign Office warns travellers to the UAE of a June 2017 announcement "that showing sympathy for Qatar on social media or by any other means of communication is an offence. Offenders could be imprisoned and subject to a substantial fine".
Mr Ahmad is said to have travelled to the UAE for a holiday. He was arrested after Qatar played Iraq in Abu Dhabi on 22 January.
According to a friend, quoted by the Guardian, the Arsenal supporter says he was assaulted by security officials after being released.
He then reportedly went to a police station to report the incident and was accused of telling lies and detained.
The UAE embassy in London said it was unable to comment specifically on the case, but "allegations of human rights violations are taken extremely seriously and will be thoroughly investigated".
A spokesman added: "As the 1.5m British citizens who visit the UAE each year know, we are a country built on the rule of law and respect for individuals."
A land, air and sea blockade of Qatar by the UAE, Saudi Arabia, Bahrain and Egypt meant there were very few fans of the Gulf state in attendance during its Asian Cup matches.
When Qatar knocked the UAE out in the semi-final, objects and shoes were thrown at their players.