Manchester City seal deal for De Jong
City's website said the 24-year-old international had signed a four-and-a-half year contract after they had agreed an undisclosed fee with Bundesliga club Hamburg SV.
De Jong, who has played 29 times for his country, joins England full back Wayne Bridge who arrived this month from Chelsea and Wales striker Craig Bellamy from West Ham United.
City, owned by Abu Dhabi billionaire Sheikh Mansour bin Zayad al Nahyan, failed this week in an audacious bid to sign former World Player of the Year Kaka from AC Milan.
However, the club's executive chairman Garry Cook said there could be more signings before the window closes.
"We've got a couple of others that we're still working on and it's unfair to comment too deeply on those," Cook told the club's website.
"We had very clear plans going into (the transfer window). We're ticking the boxes as we say."
City lie 11th in the Premier League table but only four points above the teams in the relegation zone.
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