Live television coverage of an Iranian football match was blacked-out because sections of the crowd were chanting anti-government slogans and waving green emblems in support of the country's political opposition, it was claimed yesterday.

The premier league match between Esteghlal and Steel Azin took place at Tehran's Azadi stadium just hours after tens of thousands of green-clad protesters used the state-organised Quds Day anti-Israel demonstrations to voice their opposition to the president, Mahmoud Ahmadinejad, who is accused of stealing Iran's recent election.

The game's scheduled live TV coverage was disrupted apparently after bosses of the state broadcaster, Irib, learned of the presence of protesters inside the stadium.

According to Iranian websites, the match was initially broadcast for a few minutes in black-and-white without crowd noise to show that technical problems were being experienced. The transmission then cut back to a studio presenter who said that the problems had arisen because Irib had "sent only one camera to the stadium".

Eventually the match was shown nearly an hour late, again without sound and with close-up shots focusing solely on the pitch and editing out the 70,000 spectators.

The news website Mehr described the live broadcast failure as "unprecedented". Aziz Mohammadi, the head of Iran's premier league, blamed it on Esteghlal's refusal to agree to a 15-minute kick-off delay to give extra preparation time to cameramen who, he said, had been under added pressure because of the earlier coverage of Quds Day. However, that explanation was dismissed by club bosses who said Irib had cited "technical problems" throughout the match.

The Mizan Press website – linked to the opposition National Religious party – said the real reason was the presence of supporters of Mir Hossein Mousavi, the reformist who says Ahmadinejad cheated him of victory in June.

"Following the self-motivated presence of the green wave in Azadi stadium, Irib did not cover live the Esteghlal-Steel Azin match," it wrote. "Irib's lie about camera malfunction and receiving only black-and-white images from inside the stadium was uncovered an hour later by the colour transmission using close-up and specially edited frames. In these images the spectators were not shown at all."

Suspicions that the broadcast was delayed deliberately were bolstered by reports from listeners who said they heard chants in support of Mousavi during a live radio broadcast of the game. It was the second time on Friday that TV bosses had been blindsided by opposition protests. Hours earlier, Ahmadinejad was publicly embarrassed during a live interview when opposition chants of "Ahmadi, Ahmadi, resign, resign" could clearly be heard while he was speaking.

The incident also exposed the authorities' sensitivity to expressions of dissent in sporting arenas, especially football, which has an avid following in Iran. Days after the disputed election, four members of Iran's national team were banned from the game after displaying their support for Mousavi by wearing green wristbands during a World Cup qualifying match against South Korea.

Last month eyebrows were raised when two premier league teams abandoned their green strips and took the field against each other in predominantly white outfits. The green shirts of the women's national team were withdrawn and replaced with red tops on the eve of the recent Asian Games championship in Thailand.

The authorities are understood to be gearing up for a further security crackdown this week as university students return for the start of the new academic term.