Magpies boss was at the Amsterdam ArenA to see Ajax beat De Graafschap with his sights set firmly on the Belgian defender, who is also on the radar of Arsenal and Tottenham
The Belgian has been monitored by Arsenal and Tottenham, and has expressed an interest in joining international team-mate Thomas Vermaelen at the Emirates Stadium.
But Vertonghen also told Goal.com he believes Spurs is an "amazing club."
Vertonghen's contract at Ajax will enter its final year in the summer and the Dutch side will be keen to cash in on one of their top players.
Newcastle have also been linked with FC Twente centre-back Douglas and Erik Pieters, PSV Eindhoven's Netherlands international left-back.
The Magpies have successfully plundered the Dutch market over the years, with key players Tim Krul and Cheikh Tiote signing from Den Haag and Twente respectively.
Newcastle have also shown a knack for picking up affordable, top-quality signings from Europe in recently, investing the £35 million they received for Andy Carroll on first-teamers like Yohan Cabaye, Hatem Ben Arfa and Papiss Cisse.
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