Paris Saint-German paid a world-record fee of £198m for Neymar

UEFA has opened an investigation into Paris Saint-Germain's transfer dealings with regards to Financial Fair Play (FFP) rules.

But PSG say they are "surprised" by UEFA's decision and have "always operated with total transparency".

The Ligue 1 club paid a world-record fee of £198m to sign Neymar from Barcelona last month and agreed a season-long loan for Kylian Mbappe that contains an obligation to buy the forward for £165m in 2018.

FFP rules require clubs to more or less break even over a period of three years and PSG will pay Neymar £515,000 per week over the course of his five-year contract, which could take the total cost of the Brazilian to £500m.

France star Kylian Mbappe joined PSG on a season-long loan with "option" to buy

PSG accrued about £50m from selling players this summer and UEFA says it will put the club's books under meticulous scrutiny over the coming months.

"The investigation will focus on the compliance of the club with the break-even requirement, particularly in light of its recent transfer activity," a statement read.

How Financial Fair Play works Clubs can spend up to €5m more than they earn every three seasons Losses can be covered by the club owner, up to a limit of €30m Punishments for breaching FFP rules range from a warning to withdrawal of titles

"In the coming months, the Investigatory Chamber of the UEFA Club Financial Control Body will regularly meet in order to carefully evaluate all documentation pertaining to this case.

"UEFA considers Financial Fair Play to be a crucial governance mechanism which aims to ensure the financial sustainability of European Club Football."

Sources close to the deal for Mbappe are understood to have still had reservations about whether the transfer would be signed off on Deadline Day, and questioned how PSG could make it work within UEFA's Financial Fair Play regulations.

Sky Sports News understands PSG have committed to buy Mbappe for €180m (£165m) after his season-long loan expires on June 30 next year, although this is disputed by one club source.

The final deal will be scrutinised by UEFA, who cannot block any transfers.