A furious Mikel Arteta described Arsenal’s defeat against Inter Milan as “very, very difficult to accept” – and said his side should have been awarded a penalty after Mikel Merino was “punched” in the head.

Arsenal fell behind on the stroke of half-time when Inter were awarded a contentious penalty after Merino was adjudged to have handled the ball in the area.

Merino might count himself unfortunate given he could do little to get out of the way of Mehdi Taremi’s flick-on. Hakan Calhanoglu converted the ensuing spot-kick to send the Gunners to their second defeat in four days.

Earlier in the opening period, Merino had his own penalty claim when Inter goalkeeper Yann Sommer delivered an unintentional right hook to his head.

Asked for his reaction to the hosts’ spot-kick, Arteta said: “I don’t understand. There is no danger at all. You cannot react because the ball is very close.

“We were told at the start of the season that wasn’t a penalty. That was clear. Today it was a different story. But OK. They decide that is a penalty.

“But if that is a penalty then the one on Mikel Merino where he punches him in the head has to be a penalty, 1,000 per cent. These are the margins in this game and it’s very, very difficult to accept.

“I am extremely frustrated because these are two decisions that marked the course of the game. Unfortunately there is nothing we can do. We have to accept it and move on.”

The defeat in the San Siro marked Arsenal’s second in a row after their 1-0 loss at Newcastle last weekend which cast them seven points adrift of Premier League table-toppers Liverpool.

Arsenal dominated large spells of Wednesday’s fixture, but they failed to find a breakthrough against a side which has not conceded in the Champions League so far. It leaves the Gunners, who face Chelsea at Stamford Bridge on Sunday, 12th in the 36-team league.

But Arteta added: “This is the way I want to see my team. Of all the big games we have played in Europe, this is by far the best one that we have played in the last few years.

“If we play the way we played here we have a good chance to win against Chelsea. I told them I’m proud of them.

“I haven’t seen them play in Europe in the manner they have today. And we are very disappointed because we didn’t get what we wanted out of the game that’s for sure.”

Declan Rice was sorely missed in the San Siro – absent after he picked up a foot injury against Newcastle.

And while captain Martin Odegaard ended his two-month absence with a late cameo, Kai Havertz was involved in a clash of heads with Yann Bisseck and is a doubt for Arsenal’s trip to Stamford Bridge.

“Kai has a big cut,” said Arteta. “He had to come off because he needed some stitches. Hopefully he will be OK for the weekend.”