The Belgian's arrival would add to the uncertainty surrounding Magpies' goalkeeper Tim Krul, who's been linked with a move to Everton.
Sels in action during Gent's 2015-16 Champions League campaign
HITC reported on Sunday that Boro were leading the chase for Sels, however, the 24-year-old is due to fly to Newcastle today ahead of completing a move to St. James' Park, according to the Chronicle.
The Magpies are said to be paying around £4.5 million for Sels, who would become Rafa Benitez's first signing at the club.
Is Krul on the way out?
The Belgian's arrival would add to the uncertainty surrounding the future of Newcastle number 1 Tim Krul, with Everton being tipped to move for the Dutchman.
Krul spent much of the 2015-16 campaign sidelined, but is said to have been identified as Tim Howard's replacement by compatriot Ronald Koeman, who took over at Goodison Park earlier this month.
Sels was crowned Belgium's goalkeeper of the year last season as Gent qualified for the Europa League's third qualifying round.
However, his form was unable to land him a place in Marc Wilmots' squad for the European Championship and he looks set to spend the coming campaign in England's second tier.
Sels would be Benitez's first Magpies signing