Inter Milan ultras look to have sent a threat to the club's owners with Romelu Lukaku's future in the balance amid interest from Chelsea.
The Belgian has spent the last two years at the San Siro and has established himself as one of Europe's leading forwards.
Thomas Tuchel wants to add a top class striker to his ranks this summer and has made Lukaku his No 1 target.
Lukaku was instrumental in Inter's Serie A triumph last term and fans will be loathed to see him leave.
Reports claim, after several rejected bids, that the Italian champions are ready to cash in for £100m.
But a banner has been placed outside the club's headquarters that reads: "To the club, watch out…promises must be maintained."
It’s believed that Inter ultras representing the Curva Nord were behind the sign amid growing tensions.
Club CEO Beppe Marotta claimed earlier this summer that the striker would not be offloaded.
He said: “From our side, we can yes absolutely, Lukaku is not for sale. Lukaku is an important piece on the chessboard available to Simone Inzaghi.”
Inter are in a difficult place financially which has already seen Antonio Conte leave his post at the San Siro.
He had issues with the club's transfer policy having previously clashed with the Inter hierarchy over other issues.
The sale of Achraf Hakimi to PSG generated £51m but was immensely unpopular yet fans have been told that further departures could happen before the end of the window.
Inter begin the defence of their Scudetto at home to Genoa in just under three weeks’ time, but Chelsea are looking to take advantage of the uncertainty surrounding the club.
Tuchel inherited a squad last season that had been build by Frank Lampard with Timo Werner their main marksman, but he struggled in his debut year which has forced the Blues back into the market.
Erling Haaland was heavily linked with a switch to Stamford Bridge but Borussia Dortmund are refusing to entertain his sale.
It means attention has turned to Lukaku, who previously spent a small part of his career in west London.
Chelsea added the striker from Anderlecht as a teenager but loaned him out to West Brom and then Everton before the Toffees signed him permanently.
He has gone on to be prolific in Merseyside as well as Manchester and Milan and could now return to the European champions.
