The world governing soccer body has confirmed they are looking into the transfer following a complaint from the player's former team Sampdoria.

The 25-year-old joined United from Sporting in January for an initial fee of 55 million euros ($59.39 million) and has registered three goals and four assists in nine games.

Sky Sports reported Italy's Sampdoria had inserted a 10 per cent sell-on clause on any profit Sporting make on Fernandes, after selling him in 2017.

But the Portuguese club say that clause is null and void as the playmaker signed a fresh deal in June 2018 after terminating the original one.

"We can confirm that on April 3 the Italian club Sampdoria lodged a claim with FIFA against the Portuguese club Sporting Clube de Portugal related to financial obligations set out in the contract corresponding to the transfer of ... Fernandes," FIFA said in a statement released to British media.

Fernandes was one of a number of players who terminated their contracts at Sporting after a group of some 50 masked men attacked players and staff at the club's training complex in 2018.

He later decided to remain with the club.

Meanwhile, the Red Devils have confirmed an agreement is in place to sign 16-year-old Sunderland teenager Joe Hugill.

Hugill, who has been playing up to under-23 level with Sunderland, had reportedly attracted interest from the likes of Arsenal, Tottenham, Wolves and Leeds.

Australian Associated Press