It was announced on Monday that the Feyenoord defender was travelling to Rome to put the finishing touches to a move.
Manchester United were also reported to be in the hunt for the 22-year-old, with former Dutch national team coach Louis van Gaal eager to bring in players he knows.
However, reports in Italy suggest that Lazio have already agreed a five-year contract with a player who will cost around 9million euros (£7.1m).
Lazio coach Stefano Pioli told Lazio Style Radio: “I cannot wait to meet him and train him.”
Director of communications Stefano De Martino added: “We welcome with joy the best defender at the World Cup.
“He is an international-level signing.”