Mikel Arteta was left fuming after a controversial penalty for Inter ended Arsenal’s unbeaten record in the Champions League.

The Arsenal manager felt that his side should also have been awarded a spot kick after Mikel Merino was “punched in the head” by Inter goalkeeper Yann Sommer just before the Spain midfielder was penalised for a handball inside his own area.

Hakan Calhanoglu stroked home his 19th successful penalty from 19 attempts to give Simone Inzaghi’s team a slender victory after they survived an Arsenal onslaught in the second half. But while he was pleased with the performance, Arteta admitted he was left confused by the Romanian referee Istvan Kovacs’ decision to award the penalty.

“We were told at the start of the season that wasn’t a penalty – that was clear. But today was a different story,” he said.

“I don’t understand – it’s just a deflection. There is no danger at all and he cannot react because the ball was so close. They decide that is a penalty but then if that is a penalty then the one on Mikel Merino, when he punches him in the head, has to be 1,000% a penalty. These are the margins in this game so it’s very hard to accept. There’s nothing unfortunately that we can do and we’re not going to be able to change it.”

Merino was replaced at half-time after Arteta felt he had been affected by the clash with Sommer, while the Germany forward Kai Havertz had to be withdrawn late in the game after sustaining a cut to his head that required stitches.

Both are expected to be fit for Sunday’s trip to Chelsea in the Premier League, when the Arsenal manager should also be able to call on captain Martin Ødegaard after his long-awaited return to action after injury as a late substitute here.

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But despite suffering a second successive defeat, Arteta felt that Arsenal deserved more. “For sure this is the way that I want to see my team,” he said. “Of all the big games that we have played in Europe this was by far the best one we have played in the last few years.”