The 28-year-old has won 45 caps for Portugal and started in the final as the country won the 2016 Euros but he was not part of the Euro 2020 squad.
He joined Inter in 2016 for a reported fee of 45 million euros (50.3 million dollars) and made 64 appearances but also went out on a series of loans. He spent time at West Ham in 2017-18 and at Lokomotiv Moscow in 2019-20.
Last season he was sent out to Sporting and helped Lisbon’s other big club win a first Portuguese league title in 19 years.
Portuguese media reported that Sporting, who wanted to keep the player and had made an offer to Inter Milan, will challenge the transfer in court, alleging fraudulent practices.