Ronaldo accused the north Atlantic nation, population 323,000, of having a "small mentality" after celebrating a point in Saint-Etienne.
He said: "I thought they'd won the Euros the way they celebrated at the end, it was unbelievable.
When they don't try to play and just defend, defend, defend, this in my opinion shows a small mentality and why they are not going to do anything in the competition.
"It was a little bit frustrating, we tried hard to win the game, Iceland didn't try anything," Ronaldo added.
"They scored a goal, they created two chances in the 90 minutes and otherwise they got every player behind the ball, they put the bus in the net, so it's difficult when one team don't try but Portugal try and play football and try to win the game."
Ronaldo struggled to escape the attentions of marker Kari Arnasonof - a Rotherham United player - and missed a straightforward headed chance to win the game late on.
He was clearly angry after the match, and indeed was accused of failing to shake hands with Icelandic players after the final whistle.
After his initial unguarded outburst to the media, he seemed to calm down a bit and trot out the sort of inane platitudes which have characterised almost all the post-match reaction at Euro 2016 so far.
"It's a bit frustrating for us but it's just the beginning for us, we're not worried about that," he said.
"If you see Spain, France, they are the strongest teams in the tournament and had a difficult time to win their games so for us it was tough but we are confident. We're 100 percent confident we'll win our next game."
Cristiano Ronaldo during Portugal's game against Iceland
Image credit: Eurosport
IS RONALDO RIGHT?
Yes and no. Iceland sat back, but equally it was a typically exasperating display from Portugal, and one which only enhanced their reputation for producing technically gifted players who do not quite live up to their reputations at big tournaments.
After a nervy start Portugal gradually imposed themselves and seemed to have done the hard part when Nani put them ahead just after the half hour. But they began the second half with an air of complacency and left Birkir Bjarnason unmarked to sweep home Iceland's 50th-minute equaliser.
Cristiano Ronaldo in action against Iceland
Image credit: Reuters
After that Iceland were able to pack their defence, harry their opponents and play on their increasingly frayed nerves. They even managed to get forward and create further chances by exploiting Portugal's discomfort with high balls into the area.
Despite enjoying a whopping 72 percent possession Portugal struggled to create openings and, crowded out, Ronaldo was left to remonstrate with the referee at the final whistle.
ICELANDIC VIEW: 'JUST A SORE LOSER'
Iceland's Kari Arnason hit out at Ronaldo's comments:
"He’s just a sore loser,” Arnason said. “He didn’t want to lose the game. What does he expect - for us to play like Barcelona against him? He fannies about and dives around.
“Obviously we were the underdog, we played like the underdog and we were unlucky not to win the game.”
Iceland's coaching staff saw things differently as well.
"You can't put one player down to stop a guy like Ronaldo. It has to be a team effort, closing the areas," said Iceland's co-coach Heimir Hallgrimsson.
"There were a lot of players responsible for Ronaldo tonight. We did a really good job."
HAVE YOUR SAY
Reporting via Alex Chick / Toby Keel / Reuters