The 20-year-old has signed a five-and-a-half-year deal and will remain at the Belgian champions on loan until the end of the season.

De Bruyne, who is predominantly a left-sided player, has been on Chelsea's radar for some time and has played twice against the London club in this year's Champions League group stages.

A statement on Genk's website read: "The transfer of Kevin De Bruyne to Chelsea has been completed. He has signed for five and a half seasons and will continue (playing with) Genk until June.

"His signature was confirmed at 0.30 last night. De Bruyne and his agent will return back today from London, along with general director Dirk Degraen.

"Genk will hold a press conference with (director) Jacob Gunther and Dirk Degraen in which they will clarify the transfer policy.

"Afterwards, Kevin De Bruyne will also give an explanation about his transfer to the English club."

De Bruyne becomes Chelsea's second purchase of the transfer window following the arrival of England centre half Gary Cahill from Bolton earlier this month.

The midfielder joined Genk at 14 and quickly rose through the ranks. He made his international debut for Belgium in 2010 and is seen as one of the brightest young prospects in the country.

He is the third Belgian player signed by manager Andre Villas-Boas following the arrivals of Romelu Lukaku and Thibaut Courtois last summer. Villas-Boas admitted last Friday that De Bruyne was a Blues target even before he took the helm at Stamford Bridge last summer.

"It's a target that's decided by the club, that I knew about for quite some time," he said in a press conference.

"He was under the scrutiny of the club for some time. We've been following this player.

"[Romelu] Lukaku the same, and Petr Cech was the same when we arrived in 2004.

"In the sense that it's the club policy for the future. It's the right thing (to buy him) and I'll do everything in my power for him to reach maximum potential.

"But it's down to the club in decision-making."

Chelsea, who play Swansea tonight at the Liberty Stadium, have also been linked with Shakhtar Donetsk midfielder Willian this month, although Villas-Boas admitted last week that a move for the Brazilian is unlikely ahead of tonight's 11pm deadline.

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De Bruyne could not hide his delight at securing a move to Stamford Bridge, telling the club's website: "Three years ago I was playing with the young guys in Genk, but now I am making a transfer to Chelsea. It's almost impossible - a real dream come true.

"To come to a team like Chelsea is a dream but now it's a reality and I have to work hard to achieve the level that's necessary.

"It's a few steps (up). Chelsea is one of the biggest clubs in the world and if you see the level they have compared to Genk then it is a real difference but it's something I want to achieve and I will work very hard to get there."

The player will have to be patient to earn a first-team place at the Blues, and accepts he may have to spend next season on loan before challenging for a regular place.

He added: "I signed now and now I will go back for six months on loan to play some games and gain more experience.

"Next season it would be normal to be loaned out, but I will start the preparations here at Cobham, and if it goes really well maybe I will stay but probably it will be a team a little level less than Chelsea but bigger than Genk.

"I am patient. It will be very hard to play in the beginning but if you can train with these guys you will get to a better level than in the Belgian league for sure."

De Bruyne, whose mother was born in Ealing, west London, is a big fan of the Barclays Premier League and revealed that he grew up supporting Liverpool.

He said: "I have always followed it because my mother is half English and we probably followed it more than Belgian football so I know a lot about it.

"When I was young in my family we liked Liverpool but in the years I have been playing that has become less and when you become a professional you stop really being a fan of any team."

Meanwhile, Chelsea also confirmed this morning that 18-year-old Austrian youth international Philipp Prosenik has joined AC Milan on a permanent deal.

The midfielder arrived at the Blues from Rapid Vienna in 2009 but did not make a first-team appearance at the London club.