Lawyers for an Egyptian poet and activist who has been allegedly detained and held in solitary confinement without charge in the United Arab Emirates for over 100 days have filed a legal challenge in the U.K. against UAE authorities.

The filing was made Friday on behalf of Abdulrahman al-Qaradawi, an outspoken critic of Egypt's government who had been residing in Turkey. It urges London's Metropolitan Police to launch a criminal investigation into the activist's alleged abduction, torture and extradition to the UAE.