Iranian security forces have beaten football fans chanting anti-government slogans at Tehran’s main sports stadium, in the first such confrontation since nationwide protests began last December.

Friday’s incident happened at Azadi Stadium in the Iranian capital as fans gathered in the stands several hours before home team, Esteghlal, was due to kick off against visiting team Tractor Sazi of the northwestern city of Tabriz.

In a video clip verified by VOA Persian and received from a fan who was at the stadium, red-shirted fans of Tractor Sazi repeatedly chanted “Death to the dictator,” a popular slogan of recent anti-government street protests by Iranians who blame Supreme Leader Ayatollah Ali Khamenei for Iran’s worsening economic problems.

WATCH: Fans of visiting team Tractor Sazi of Tabriz chant "Death to the dictator" ahead of a match at Tehran's Azadi Stadium, Aug. 10, 2018.

In other footage from the stadium shared on social media and verified by VOA Persian, blue-shirted fans of Esteghlal could be seen joining in the “Death to the dictator” chants.

Video clips also showed Iranian security forces beating fans in the stands in response to the chants and several of those fans tending to wounds from the beatings. There were no immediate reports about the stadium confrontation in Iranian state media and no official word on how many people were wounded or arrested.

It was the first time such scenes have unfolded at Azadi Stadium since Iranians began frequent street protests across the country last December, expressing anger toward local and national officials and business leaders they accuse of corruption, mismanagement and oppression.

In another highly unusual move, social media photos verified by VOA Persian showed that Iranian security forces deployed a military vehicle inside the arena in an apparent attempt to quiet the protesting fans.

Stadium authorities brought the situation under control and the regular-season match began on schedule. Esteghlal went on to beat Tractor Sazi 3-0.

But some observers noticed that the Iranian state TV network broadcasting the match repeatedly lowered the volume of the audio feed from the stadium when fans began to chant. They said it appeared that the broadcaster was trying to stop viewers from hearing those chants.

This report was produced in collaboration with VOA's Persian service.