"One of the most prolific strikers in European football, Lukaku has returned to the club he supported as a young boy and where he has unfinished business, having been on our books between 2011 and 2014," the team said in a statement.

"I’m happy and blessed to be back at this wonderful club,’ said Lukaku.

'It’s been a long journey for me: I came here as a kid who had a lot to learn, now I’m coming back with a lot of experience and more mature," he added.

Lukaku previously played for Belgium's Anderlecht, Italy's Inter Milan, and several English clubs, including Manchester United, West Bromwich Albion, and Everton.