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.

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.

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.

His third goal of the season was followed by a clutch of good chances for the away side who were denied a leveller in the second half by a combination desperate defending and one spectacular Yann Sommer save on Kai Havertz.

Inter now face Serie A leaders Napoli on Sunday with the chance to move top after five of Simone Inzaghi's first-choice players -- including Italy stars Nicolo Barella and Federico Dimarco and France forward Marcus Thuram -- started Wednesday's match on the bench.

Arsenal face Chelsea at Stamford Bridge as they try to snap a run of three Premier League matches without a win and get a faltering season back on track.

Arteta will be able to count on his skipper Martin Odegaard after the Norway international made an appearance as a late substitute for Havertz.

Odegaard had missed Arsenal's 12 previous matches after picking up an ankle injury with his country, and his return is a boost for Arteta who is also sweating on Declan Rice who played no part at the San Siro.