Former Portugal international Fernando Meira has criticised Cristiano Ronaldo's decision to walk off the pitch and throw away his captain's armband and said the it was "unacceptable" behaviour.

Ronaldo stormed off the pitch before the final whistle was blown after he was denied a clear winner in a controversial end to Portugal's 2-2 draw with Sebia in their World Cup Group A qualifier.

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Serbia defender Stefan Mitrovic had chased down Ronaldo's shot and attempted to clear it off the line but despite his efforts it had crossed into the goal. However, referee Danny Makkelie waved on play and there was no VAR or goal line technology to check the call.

"It's a clear goal but Ronaldo cannot throw Portugal's captain's armband on the floor." Meira, who has 54 Portugal caps, said after the game.

"Cristiano's reaction is natural but unacceptable for the captain of the national team. You cannot throw the captain's armband on the floor and go towards the changing room while the game is still going on.

"It's not acceptable for a player of his importance. I understand his frustration and I agree with him because the goal was valid but the referees are the ones that have to make decisions, without VAR, and he has to set an example. And yesterday's was not one to follow."

Portugal coach Fernando Santos was less concerned about his captain's reaction and said it showed "normal frustration" at the situation.

"I don't know what happened, I was told he reacted badly. It's the normal frustration of someone who scores the winning goal for Portugal and it doesn't count. I will not go into it any further," Santos added.

"The referee apologised and told me that he was ashamed. I was in the changing room with him and he apologised. He told me on the pitch that he was going to look at the images and if it was the case, he would call me to apologise... and that's what he did."

Ronaldo's sisters also posted messages of support for their brother on Instagram.

"This is what is called love for your country, love for your jersey," Katia Aveiro said on Instagram.