Liverpool register interest in Newcastle's Alexander Isak - source

Liverpool have registered their interest in signing Newcastle United forward Alexander Isak this summer as they continue their search for a No. 9, a source has told ESPN.

The Premier League champions are in the market for a new centre-forward as uncertainty over the future of Darwin Nunez continues, with Napoli one of the clubs interested in signing the Uruguay international this summer.

Liverpool also turned down a €67.5 million (£78.5m) bid from Bayern Munich to sign forward Luis Díaz on Tuesday. The Reds have not submitted a formal offer for Isak however they have made an approach to Newcastle to assess his availability, as they have done with other forward targets.

Newcastle's stance has so far been that they are unwilling to let the Sweden international -- who has scored 62 goals in 102 appearances for the club -- depart this summer.

Liverpool have already broken their transfer record to sign Bayer Leverkusen playmaker Florian Wirtz in a deal that could rise up to a British-record £116m. It will likely take more than that for Newcastle to sanction Isak's exit this summer.

Sources have also told ESPN Newcastle are working on a deal to sign Eintracht Frankfurt forward Hugo Ekitike, with a view to the forward playing alongside Isak in attack.

Liverpool have also been liked with the player however it is understood they are not convinced by the 23-year-old, with Newcastle set to up their offer to Frankfurt in the coming days.