A late own goal by Morocco handed Iran on Friday victory in their opening match at the FIFA World Cup.
Aziz Bouhaddouz gifted Iran a dramatic 1-0 victory, sending euphoric Iranian players on to the pitch.
It was Iran's second win in 13 matches at the World Cup, and Asia's first since the 2010 tournament in South Africa.
Wasteful finishing looked to have consigned this compelling contest at the Saint Petersburg Stadium to a goalless draw but Bouhaddouz's mistake in injury-time means Iran emerge as the early challengers to Spain and Portugal in Group B.
Morocco was most dangerous on the wings, through Hakim Ziyech on the right and Amine Harit on the left, during its strong start to the game.
Iran coach Carlos Queiroz, once of Real Madrid and Manchester United, insisted the chaos that has engulfed Spain this week offered no boost to these teams' chances, but this victory certainly cranks the pressure up a notch.
When Bouhaddouz nodded in at the near post, Iran's substitutes could not resist rushing onto the field and when the final whistle blew moments later they were sprinting over again in delight.
Morocco should at least take heart from a blistering first half an hour, during which their zip and zest deemed them virtually unplayable. But Ziyach, Ayoub El Kaabi and Mehdi Benatia all failed to capitalize.
Morocco's fans, at a World Cup for the first time in 20 years, belted out their own national anthem and then applauded Iran's, the 67,000-seater arena a sea of red and white, and buzzing with the hum of vuvuzelas in a throwback to the 2010 World Cup in South Africa.
The only shame was the large number of empty seats at kick-off, with many supporters still queueing to get through security 15 minutes before kick-off.
Morocco started brilliantly, hounding Iran's every touch and swarming forward with such ferocity that on the line, Queiroz spent most of the opening 20 minutes urging his players to pause and take a breath.
The only surprise was Morocco were not ahead as Ziyach kicked the air from a well-worked corner, El Kaabi sliced wide and a penalty-box scramble saw shots from Younes Belhanda and Benatia blocked.
The onslaught finally eased after half an hour and by the interval Iran had not only survived but finished the stronger, Sardar Azmoun, the 'Iranian Messi', spurning a one-on-one after a scintillating break.
Perhaps tired from the first period or, more likely, reminded of their defensive duties during the interval, both teams were cagier after the restart.
They each made substitutions as the game drifted past the hour and the closest it had come to a winner was when a fizzing Ziyach drive had to be tipped around the post by Ali Beiranvand.
Queiroz and his opposite number Herve Renard were involved in a touchline scuffle, that was quickly resolved, before the real drama arrived moments later.
Bouhaddouz could not see what was behind him when a whipped free-kick came in from the left and he panicked, diving to the ball and heading it inside his own near post.
