Dutch international defender Virgil van Dijk could become the world's most expensive defender and join English Premier League giants Liverpool from rivals Southampton, according to British media reports.

The 25-year-old -- who joined Southampton in 2015 after impressing at Scottish champions Celtic -- would cost around £60 million (69m euros, $77m), according to reports.

However, BBC Radio Solent and other media outlets reported later on Tuesday Southampton were unhappy and had asked the Premier League to probe whether there had been an illegal approach by Liverpool.

Van Dijk would be Liverpool's most expensive ever signing -- striker Andy Carroll having cost £35 million in moving from Newcastle United in 2011.

Celtic would be in line for 10 percent of the fee having included a sell-on clause in his transfer to Saints.

David Luiz is presently the most expensive defender in the world having been sold to Paris Saint-Germain by Chelsea for £50 million in 2014.

According to The Sun, Liverpool manager Jurgen Klopp has convinced the Liverpool owners Van Dijk is deserving of earning a weekly wage of almost £200,000 (230,000 euros, $258,000) -- which will make him their highest ever paid player.

Van Dijk -- who also caught the eye of both Manchester City and champions Chelsea -- is keen on a move to Liverpool not only for Champions League football but to join compatriot and close friend Georginio Wijnaldum.

Southampton have become a favoured hunting ground for Liverpool in the past three years having signed five players -- including Adam Lallana and Senegalese star Sadio Mane -- for a total of almost £100 million.