NAPLES, Italy (Reuters) - Gonzalo Higuain was a distant memory as Napoli produced a rousing display to beat last season's quarter-finalists Benfica 4-2 in the Champions League on Wednesday.

Midfielder Marek Hamsik headed Napoli in front after 21 minutes before a devastating spell of three goals in eight minutes early in the second half left the Portuguese champions reeling.

Dries Mertens curled in a free kick in the 51st minute, Arkadiusz Milik swept home a penalty and Mertens struck again just before the hour.

Benfica enjoyed a late flurry with Goncalo Guedes and Eduardo Salvio making the scoreline more respectable but were unable to prevent their first defeat of the season.

Napoli, unbeaten in all competitions this season, have six points from their two games in Group B while Besiktas have two and Benfica and Dinamo Kiev one apiece.

Higuain scored a record 36 goals in Serie A last season before he was sold to Juventus for 90 million euros ($100.92 million), but his absence has been barely noticed with Napoli scoring 20 goals in eight games.

In the group's other game, Portugal forward Ricardo Quaresma scored from a free kick to give Besiktas a first-half lead in Istanbul but Kiev forced a 1-1 draw when substitute Viktor Tsygankov scored midway though the second half.

Napoli produced some flowing attacking moves although the scoreline was somewhat harsh on Benfica who created plenty of chances of their own.

The game could have taken a very different course if Kostas Mitroglou had converted either of two good early chances for the visitors, but instead Napoli took control.

Hamsik made the breakthrough when the Napoli captain got free at the near post to head in Faouzi Ghoulam's corner.

The home team enjoyed a purple patch as Mertens curled in a free kick six minutes after the break, then Benfica goalkeeper Julio Cesar upended Jose Callejon and Milik scored from the spot.

Shortly afterwards, a deep cross found Milik bounced off his back and fell perfectly for Mertens to strike again in the 58th minute.

Napoli appeared to relax and Guedes collected a misplaced pass in midfield, ran on and scored past Pepe Reina to reduce the arrears in the 71st minute.

Salvio also scored a well-taken goal with four minutes left, to give Napoli an uncomfortable final few minutes.

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(Writing by Brian Homewood; Editing by Toby Davis and Pritha Sarkar)