Iranian fans with pre-revolutionary flags are denied entry to the England game.

Iranian fans carrying the country’s pre-revolutionary flag were barred from entering their country’s World Cup game against England on Monday unless they surrendered the flags, which are viewed as a symbol of protest of Iran’s theocratic government.

The flags are similar — dominated by green, white and red bands — but while the pre-revolutionary flag has a lion and sun in the center of its white band, the Iranian national flag has an Islamic symbol and phrasing in its place.

Fans wearing shirts with the flag or other anti-Iran messaging also were not allowed inside unless they agreed to turn their shirts inside out.

On the field, Iran’s players staged their own silent protest by declining to sing their country’s national anthem.

Historically, Iran’s national soccer team, known as Team Melli, has been an entrancing and unifying force in the country. But the most absorbing part of Monday’s match may not be its play on the field, or the outcome. Instead, it might be any gestures made (or not made) by Iran’s players and spectators in support of protests that have engulfed the nation for the past two months. Demonstrators are demanding an end to the country’s authoritarian clerical rule.

“I think everyone is going to be watching the match, but for a very different reason than usual,” said Shima Oliaee, the Iranian American creator of “Pink Card,” an audio documentary premiering next month on ESPN about the decades-long attempt by Iranian women to gain full access to soccer stadiums.

“I don’t think anyone in Iran is thinking too much about who is going to win the game,” Ms. Oliaee said in an interview on Saturday. “They’re thinking about who is going to win the country.”

Iran has been inflamed since Mahsa Amini, 22, died on Sept. 16 after being arrested by Iran’s morality police on charges of violating a law requiring head coverings for women. A brutal crackdown by Iranian authorities has reportedly left more than 300 people dead, including children.

Players on Iran’s national team and in its domestic soccer league have recently become emboldened in supporting the protests by not singing the country’s national anthem and by declining to celebrate goals scored.

Iran’s captain, Ehsan Hajsafi, alluded to the protests in a prematch news conference on Sunday.

“We have to accept that the conditions in our country are not right and our people are not happy,” he said.