Sir Rod Stewart has criticised the section of Celtic fans who lit flares inside Stadio Olimpico during the Hoops' 2-1 win over Lazio.

The Parkhead club have already faced punishments for fan behaviour, with three charges against them this season alone, and were previously fined £10,400 by Uefa for fans setting off flares in the Europa League win over Cluj.

Celtic also paid an £11,000 fine for their fans using flares and then throwing objects in the play-off second-leg win over AIK in Stockholm back in August.

The 74-year-old singer, who is known to be a huge Celtic fan, fears the actions of the Green Brigade could see the club bogged down with more sanctions.

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In an exclusive with The Sun, he said: We’ve got to be careful. We don’t help ourselves.”

“I looked along at Peter Lawwell and I said ‘We’re in trouble aren’t we?’ And he said ‘Yes we are’.”

Sir Rod watched Neil Lennon’s men from the stands on Thursday with the club’s chief executive as some of the 9,000 away fans lit the flares.

It came two weeks after the Green Brigade revealed a huge banner that showed Italian fascist Benito Mussolini's body being hung after he was shot with the message ‘Follow your leader’ the last time the two sides met.

Posts from social media also appear to show fans doing handstands to celebrate Celtic’s second goal to mock Fascist dictator’s upside-down corpse.

Sir Rod said: “I think the Mussolini thing may have been over the top. The vast majority of supporters were so well behaved.

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“We were in a restaurant in People’s Square and it was a gorgeous sunny day and there were Hoops supporters everywhere.

"I was hiding away having some spaghetti and some wine when I heard these lads singing You’re In My Heart in the restaurant next door.

“They hadn’t spotted me as there was a bush between the restaurants.

“Then someone saw me, then someone else. But they were great, getting selfies for their mum and being polite.

“Then we were out on the street and did a version of Grace. The police just looked on and gave us a round of applause actually. It was really good. I was so proud of those supporters.”

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The singer also slammed fans for behaviour as reports revealed three Celtic fans were stabbed and 12 Lazio fans were arrested as fans ambushed bars.

He said: “I couldn’t have been treated better by everyone at Lazio, but it’s a bloody shame about those f****** supporters.”

He also admitted that it wouldn’t stop him from travelling to see his lifelong favourite club and spoke of his good time in Rome after traveling with fellow singer John McLaughlin.

Sir Rod continued: “Of course I was worried, but it still wouldn’t keep me away.

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“I was staying in a lovely hotel at the top of the Spanish Steps so I was pretty safe as I didn’t go in any bars. But I was out singing on the streets.”

“It is one of the most wonderful moments. We followed the team coach in and Scott Brown and Neil Lennon came over to shake hands. I said, ‘Go on Neil, let’s get a point here.’ And he said ‘We’re going to win’.

“And he was right. It was fabulous. But I had a flight booked for straight after the game, so I didn’t party on.”