When the cameras panned to the Colombian singer Shakira cheering on her footballing husband, Gerard Piqué, during a Confederations cup match, to many it was just another shot of a glamorous celebrity. But in Iran, the few seconds of a woman with bare arms and a revealing top broadcast on national television for the first time prompted furious debate.

Hardliners in Iran attacked the Islamic Republic of Iran Broadcasting (IRIB) network this week for a series of gaffes, showing "indecent" and "un-Islamic" images in the middle of its live sports coverage, including the glimpse of Shakira.

The images came as a surprise to millions of viewers. Thousands of her Iranian fans quickly posted the still images of her appearance online and tweeted their delight. "Everyone tune in to [IRIB's] channel 3, they're showing Shakira!!!," tweeted one. "Last night they showed Shakira, tonight they shall show Jennifer [Lopez]," read another tweet.

Iranian women are not allowed to accompany men in stadiums for national football matches, and international games, usually streamed from foreign-based satellite channels, are strictly moderated. But censors appear not to have had enough time to react during last week's coverage.

Another big challenge for the state TV came within a few days. This time, Iran's national volleyball team was in a rare high-profile game with Italy on Sunday in Sardinia, where high temperatures had prompted yet more spectators to wear revealing clothing. To the dismay of fans, officials at the IRIB decided to broadcast the match with a seven-second delay and repeatedly cut live coverage to show archive images in order to avoid scenes deemed inappropriate. Despite this, it was unable to black out all images, and those broadcast on national TV included scenes showing Iranian exiles with western clothing.

Both occasions prompted Ali Motahari, Tehran's conservative MP, to issue a warning to the IRIB asking it to take more care.

In response to his criticism, Ezatollah Zarghami, the head of Iran's state television, said on Tuesday that broadcasting volleyball matches was even more difficult than showing live election debates, his comments grabbing headlines in Wednesday's newspapers in Tehran.

Zarghami faces another problem on Friday for a volleyball match between Iran and Cuba.

"Because of the warm weather in Cuba, the situation is going to get even worse," he warned. "We have decided to negotiate with our cultural colleagues in Cuba in order to have fans wear tracksuit trousers and sweatshirts," he told the Mehr news agency. Zarghami's comments about talks with Cuba were taken seriously until Mehr later clarified he was joking. Zarghami said that state TV has no other way but to broadcast the match or otherwise viewers will turn to satellite channels.