Ronaldo’s strike could have won the game for Portugal; however, his shot was cleared by defender Stefan Mitrovic having already crossed the goal-line.
Television replays appeared to show the ball crossing the line but, the absence of VAR in Belgrade meant his effort had hit the rock.
Reacting to the disallowed goal, Ronaldo took to Instagram to vent his frustration: “I always give and will give everything for my country and that will never change.
“But there are difficult times to deal with, especially when we feel that an entire nation is being harmed.
“We will keep our heads up and face the next challenge now.”
Diogo Jota’s double had put the visitors in control at the break, but second-half goals from Fulham’s Aleksandar Mitrovic and Filip Kostic saw Serbia – who had Nikola Milenkovic sent off in stoppage time – draw level.