The Dutch defender has been heavily linked with a move away this summer, with Barcelona, Juventus, Manchester United and Paris Saint-Germain all expressing interest in the teenager.
De Ligt, 19, guided Ajax to the Eredivisie title, the Dutch Cup and Champions League semi-finals last season and has caught the eye with some imperious performances at the back.
The defender, who made his debut for the club in 2016, joined Ajax aged nine and has netted 13 goals in 117 games.
In a statement, the Dutch club said: “[We] left Saturday afternoon with 28 players to the training camp in Bramberg, Austria, Awaiting a possible transfer, Matthijs de Ligt does not travel with the group.”
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Last week, Barcelona president Josep Bartomeu said he knows which club the Dutchman would be playing at next season but did not elaborate further.
Juventus, who won their eighth consececutive Serie A title last season, are the clear favourites for De Ligt’s signature and are reportedly close to a £71.6m deal.
Earlier this week, reports stated De Ligt had agreed a contract with the Italian club, which would see him earn £10.8million per season.
However, the only thing holding up the deal was the two clubs agreeing on a fee, prompting De Ligt’s agent Mino Raiola to call on Ajax to seal the move swiftly.
Raiola told Dutch newspaper De Telegraaf: “Agreements have been made with Matthijs and it is up to Ajax how to deal with this.”