Millwall and Montenegro goalkeeper Matija Sarkic died on Saturday at the age of 26, the Championship club confirmed.
Sarkic fell ill in his home country while on international duty.
Montenegrin daily newspaper Vijesti reported Sarkic died in an apartment in Budva early in the morning.
"Everyone at the club sends their love and condolences to Matija's family and friends at this immensely sad time," Millwall said in a statement.
"The club will make no further comment at this time and asks that the privacy of Matija's family is respected."
"Our dear Matija, we will miss you and your cheerful spirit, your work ethic and your great defending," the Montenegro Football Association (FSCG) said in a statement, describing Sarkic as an "always smiling guy".
"On behalf of European football, our deepest condolences go to Matija’s friends, family and everybody who knew him. Rest in peace, Matija," governing body UEFA said in a statement.
"The club will make no further comment at this time and asks that the privacy of Matija's family is respected."
"Our dear Matija, we will miss you and your cheerful spirit, your work ethic and your great defending," the Montenegro Football Association (FSCG) said in a statement, describing Sarkic as an "always smiling guy".
"On behalf of European football, our deepest condolences go to Matija’s friends, family and everybody who knew him. Rest in peace, Matija," governing body UEFA said in a statement.
Sarkic made nine saves in Montenegro's 2-0 defeat to Belgium in a friendly last Wednesday and was named man of the match for his outstanding performance.
Born in Grimsby, England, Sarkic played for Aston Villa and Belgian side Anderlecht at youth level.
He made 33 appearances for Millwall after joining in August 2023 from Premier League side Wolverhampton Wanderers.
