Crystal Palace have made a £12million offer for Wolfsburg defender Maxence Lacroix and bid for Benfica centre-back Tomas Araujo.
The moves for the pair come amid a summer of change within the defensive ranks at Selhurst Park.
Palace have agreed to sell Joachim Andersen to Fulham for £30m and expect a new offer from Newcastle for Marc Guehi.
Eddie Howe's side have already seen several bids rejected for Guehi, with Palace valuing the England international at £65m.
Guehi and Andersen have generally been the first choice defensive pairing at the club over recent seasons, although Palace boss Oliver Glasner has utilised the duo in a back three in recent times.
Meanwhile, Lacroix hails from France and was signed by Oliver Glasner when he was in charge of Wolfsburg.
The 24-year-old has since gone on to rack up more than 100 appearances for the German club after coming through the youth ranks at Sochaux.
Araujo, 22, is a Portugal Under 21 international and enjoyed a breakthrough year at Benfica last season.
Palace lost their opening game of the Premier League season 2-1 to Brentford on Sunday, with Guehi and Andersen both starting at the back despite the speculation surrounding their futures.
Verissimo3
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Tomas Araujo is key at the back for Benfica. Antonio Silva is still too hot and cold to be a starter for Benfica
Verissimo3
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Tomas Araujo isn’t going anywhere just yet. Benfica want hint to stay