The Dutchman conceded there was “interest in the boy”, referencing the 19-year-old Charlton forward, who only made his professional debut in November 2015.
Lookman has scored seven goals this season for the mid-table League One side and has caps to his name at England Under-19 and U-20 level.
But Everton boss Koeman was not so willing to divulge any further information on possible targets, adding: “We are working on that. We have some interest in certain players, but we need to keep that inside.
“Some names are true, some are not true. Most of the time it’s b******t!”
The Toffees travel to Hull City on Friday and Koeman confirmed goalkeeper Maarten Stekelenburg (dead leg) and midfielder James McCarthy (hamstring) would miss out.
Hull are bottom of the table, while Everton sit seventh, but Koeman knows it would be naive to take anything for granted in the Premier League.
“[Expecting to win] is the most dangerous thing you can do,” he said. “The Premier League is unpredictable.”
