Hakan Calhanoglu fired Inter Milan to a 1-0 win over Arsenal on Wednesday to continue their unbeaten start in the Champions League and inflict a first defeat on the Gunners in this year's revamped tournament.

Turkey captain Calhanoglu rifled home the winning penalty in first-half stoppage time to put Inter on 10 points at the halfway point of the new single league phase.

Unbeaten Inter are one of four teams to sit two points behind leaders Liverpool and look a good bet to finish in the top eight places which offer direct qualification for the last 16 as they are yet to concede a goal.

"The boys were magnificent. We beat a really good team, who have been fighting with Manchester City," Inter coach Simone Inzaghi told reporters.

"Tonight was a night to remember because we played in front of a stadium which pushed us on all the way, and we deserved to bask in their applause."

Arsenal meanwhile continued their shaky run of form and sit 12th on seven points, although Mikel Arteta's team deserved more from an engaging encounter at the San Siro.

Arteta was angry at the decision to give Inter's penalty, for Mikel Merino handling Mehdi Taremi's flick, as he believed his defender couldn't get his arm out of the way.

He also couldn't believe that his team weren't given a spot-kick early in the first half when Sommer clattered into Merino -- who was substituted at half-time due to the impact -- while trying to clear the ball.

"If you are going to give a penalty, the other one has to be because he punches him in the head," he said to TNT.

"There is no deflection, nothing you can do in the box, so can he get away from it? If he is going to give that the other has to be 100 percent a penalty."

Calhanoglu's winner was the first goal Arsenal have conceded in the Champions League this campaign and came on his first start since picking up a thigh injury on international duty last month.