During his career Miller earned 21 senior caps for his country between 2004 and 2009 and scored one goal against Sweden at Landsdowne Road.
Former Celtic teammate Stiliyan Petrov, who himself battled leukaemia in 2012, said: "My thoughts and prayers are with his family and friends. His immediate family as well and friends - they'll be feeling it more so than anyone today and it's just terrible, it's just very bad when you get that text and you hear the news", he added.
But the midfielder's former clubs, including Celtic, Leeds, Hibernian and Sunderland, confirmed on Friday that he had passed away. "We extend our deepest condolences to his loved ones at this hard time", the English club said on its official website.
Minster for Sport Shane Ross paid tribute to Miller and said his thoughts were with his family. "May he rest in peace".
Celtic manager Brendan Rodgers said Miller lived the Irish dream of playing for the Parkhead club. "Thanks a million, Liam Miller". My thoughts and prayers are with his family and friends.
Former Ireland striker Clinton Morrison described his teammate as "a great guy".
Chris Sutton, who also played with Miller at Celtic, tweeted: "Terribly sad news about Liam Miller".
"I am very sad to hear that Liam has died", Ferguson said.
Kevin Kilbane tweeted that he was "taken far too soon", and added that he was "proud to have shared a dressing room with him". "The masseurs here and Kendo [first team coach and former player John Kennedy] knew him". He just missed out on Cork City's purple patch with Dundalk dominant.
"A model pro. Condolences to his family and friends".
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