"I want to say a big thank you to all the people involved at Everton. I want to thank the fans for your support throughout the 4 years we've spend together," Lukaku said on Instagram.
"You guys helped me through all my games and I can proudly say it was an honour to play in front of you. To the staff at the stadium and training ground thank you for making me feel home from the first day I walked in.
"To my teammates it was great to play with you guys... Working with you guys has been a pleasure and I'll take your advice throughout the rest of my career. Thank you Everton Football Club."
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United confirmed that they had agreed a fee for the 24-year-old on Saturday with British media reporting it to be around 75 million pounds.
Lukaku will also reunite with United manager Jose Mourinho, under whom he played at Chelsea.
(Reporting by Aditi Prakash in Bengaluru; editing by Amlan Chakraborty)
