Stephen Kenny left Serbia convinced the Republic of Ireland would not have lost their opening World Cup qualifier had they been awarded the penalty they deserved.

Kenny's men took a surprise lead in the Group A fixture at the Rajko Mitic Stadium in Belgrade when Alan Browne ended their wait for a goal after 11 hours and 18 minutes of football, but ultimately ended up on the wrong end of a 3-2 scoreline.

However, there were devastated not to be awarded a second-half spot-kick when striker Aaron Connolly went down under Stefan Mitrovic's challenge at 1-1, only for Italian referee Davide Massa to wave away his claims.

Manager Kenny, whose wait for a first victory now stretches to nine games, said: "We've had a blatant penalty rejected, absolutely. We've watched it back and Aaron has touched the ball away and Mitrovic, the centre-back, has fouled him.

"That's a penalty go to 2-1 up and we're not losing the game at 2-1 up in the second half, that's for sure. We're not saying we definitely would have won it, but I don't see us losing it.

"That's a very pivotal moment in the game."

Browne's 18th-minute header from Callum Robinson's inviting cross handed Ireland the perfect start, but Dusan Vlahovic levelled before the break before substitute Aleksandar Mitrovic took the game by the scruff of the neck.

Mitrovic had only been on the pitch for five minutes when he beat 21-year-old keeper Mark Travers, making his competitive debut for his country, with an audacious chip, and then headed his side into a 3-1 lead with 15 minutes remaining, in the process establishing himself as Serbia's joint-record international goalscorer on 38.

Fellow substitute James Collins reduced the deficit four minutes from time, but a late flurry of activity failed to produce an equaliser.

Kenny said: "The concession of the second goal is a disappointing goal, we know that and then the third goal, we're wondering how we're 3-1 down.

"I felt all of the substitutes made an impact – James Collins got the goal back and it's a late rally for the equaliser, which we don't quite get.

"We're disappointed to lose the game, really, and it hurts. Serbia are a very good team with a lot of very good attacking players, but we feel disappointed to lose."