An Iranian wrestler says his managers told him to intentionally lose to a Russian competitor to avoid facing an Israeli wrestler in the next round.
He says: "In a moment, my whole world seemed to come to an end."
Israel and Iran are bitter adversaries and Iranian athletes traditionally refrain from competing against Israelis. Iran's government usually rewards such behavior.
Karimi says he was beating Russian Alikhan Zhabrailov when coaches told him to lose.
Iran's sport ministry in a statement praised Karimi for supporting "human values."
The country does not recognize the Jewish state, placing it in the same "Great Satan" category as the United States, and forbids its sportsmen from competing against Israelis.
The story of wrestler Ali Reza Karimi Mashiani has struck a chord on social media, with many in Iran backing his stance but some also opposing it.
His bout was in the Polish city of Bydgoszcz on Saturday, in the 86-kilo category of the under-23 world championships.
The hashtag #youmustlose was trending Monday in Iran, with comments both for and against his actions, some of them hostile to Iran's authorities and others saluting his stance.
While he may have forfeited a podium place in the tournament, Karimi Mashiani did receive the backing of his government and the Iranian wrestling federation.
"Your noble and heroic action in the world competition in Poland, abandoning the medal and the podium in support of the highest human values, is a source of pride and praise," an official statement on the website of the youth and sports ministry said, addressing the young wrestler.
The country's wrestling federation in its own statement called him a "hero" and extolled his "sacrifice," hinting that he had acted in a similar manner previously in 2013.
"It is the second time that you have risen up against the oppression of the Palestinian people by abandoning your rights in an act of absolute submission," the federation wrote.
Quoted by the ISNA news agency, the coach of the national free wrestling team, Mohammad Talaie, called Karimi Mashiani a "deserving young man" and appealed for this to be recognized by the authorities.
But among the many indignant tweets was one from reformist MP Mahmud Sadeghi, who said: "It is not difficult not to face an opponent so you do not recognize the false identity of his government," but "it is very difficult to be forced to weakness and forced to defeat a rival."
"If he decides to go fight in the colors of another country, no one can say he sold out his homeland," said another tweet.
Another railed: "Do the authorities not say that Israel is evil? Instead of running away, let us rise up and fight and defeat them."
According to the results of the tournament, Russia's Zabrailov won gold in the 86-kilo category and Israel's Uri Kalashnikov took the third step of the podium.