Viktor Klonaridis's second-half double looked to have clinched a share of the spoils for AEK, which had taken full advantage of Ruben Dias's red card late in the first half.

Yet Benfica,  2-0 up by the 15th minute thanks to Haris Seferovic and Alex Grimaldo, rallied through substitute Semedo's solo effort on his debut in the Champions League proper.

The victory ends Benfica's eight-match losing streak in the competition, getting it off the mark in a tightly-contested Group E.

Benfica was ahead inside six minutes, Seferovic reacting sharply to tuck home on the rebound after Vasilios Barkas parried Gedson Fernandes's strike.

AEK was carved open again not long after, Grimaldo making no mistake with a neat header from six yards.

The host was handed a boost on the stroke of half-time, however, when Dias picked up a second booking for a high kick on Ezequiel Ponce.

Dias's recklessness was soon punished - Klonaridis getting the better of his marker to turn in Niklas Hult's low cross.

AEK's pressure told again after the hour, Marios Oikonomou's knock-down leaving Klonaridis with a simple finish.

Klonaridis should have completed the turnaround with 19 minutes remaining, only to fire straight at Odisseas Vlachodimos, and Semedo soon made the host pay.

Having picked up the ball inside Benfica's half, the youngster powered through AEK's midfield before dispatching coolly to clinch the points.