Arsenal reportedly sent scouts to watch Gelson Martins in action for Sporting CP on the weekend.

The 21-year-old winger is already being watched by the likes of Manchester United, Manchester City and Real Madrid but it is understood that the Gunners are now showing significant interest.

Portuguese newspaper A Bola reports that scouts from Premier League pair Arsenal and United saw Martins supply an assist for Bas Dost's winning goal at Boavista on Saturday.

It is believed Sporting are bracing for the imminent exit of their star youngster even though he said last month that he was 'only thinking of Sporting'.

The interested clubs are likely to enter a bidding war for the Cape Verde-born, three-time Portugal international in January.