Osimhen scored just six minutes before the final whistle to seal the victory for Napoli at the Diego Armando Maradona Stadium.
The victory sent Napoli top of Group A with a 100 per cent record and 11 goals difference.
Liverpool defeated Ajax 2-1 at Anfield to record their first victory in the competition.
Bassey’s Ajax thrashed Rangers 4-0 while Osimhen’s Napoli hammered Liverpool 4-1.
Napoli top the Serie A table as one of six teams with seven points from three games.
Napoli have now won for the first time since the start of April, having lost to Fiorentina and Empoli and drawn at home to AS Roma.
Napoli are currently second on the Italian Serie A log with 63 points in 30 games, trailing League leaders AC Milan.
Spanish side Barcelona booked their place in the round of 16 of the Europa League, beating Napoli 4-2 win on Thursday.
Napoli held on as they were bombarded in the last 10 minutes, with Torres and substitutes Luuk de Jong and Ousmane Dembele missing chance after chance in front of Alex Meret’s goal.
Napoli will face league leader Inter Milan on Saturday with an expectation to displace Inter from the top spot.
