Jagiellonii Bialystok claim Swansea City have made a 'concrete' offer for highly-rated goalkeeper Grzegorz Sandomierski.
The 21-year-old has attracted interest from several clubs across Europe, with Chelsea and Juventus rumoured to be among his admirers.
Sandomierski helped Jagiellonii to win the Polish Cup and has also impressed when called upon for the Poland national team.
His agent revealed earlier this month that an unnamed club had made a bid for the keeper and Jagiellonii say it is Premier League new boys Swansea who have stepped up their interest.
A Jagiellonii spokesman told Polish sports daily Przeglad Sportowy: "On Monday, we received a concrete offer from Swansea. For several weeks they have been very determined to buy Grzesiek."
Any move for Sandomierski is likely to raise further doubts over the future of Dorus de Vries at the Liberty Stadium.
The Dutchman has been considering a new contract at Swansea, with Wolves among the clubs said to be interested in recruiting the 30-year-old.