Meta on Thursday said that tens of millions of people in Iran are using Instagram despite government efforts to block the service due to months-long protests.

Iran has been rocked by citizen outrage since the September 16 death in custody of 22-year-old Mahsa Amini following her arrest for an alleged breach of dress rules for women.

"Instagram has been widely used by Iranians to shed light on the protests and the brutal response to them," Meta president of global affairs Nick Clegg said during a briefing.

"People have also shared Instagram footage of the protests with international media outlets, many of whom can't report directly from Iran."

Protests triggered by Amini's death resulted in authorities clamping down on speech and freedom of assembly, and limiting the use of the internet and apps such as Instagram, Clegg noted.

"Despite attempts to block Instagram, we're seeing tens of millions of people still finding ways to access it," Clegg said.

Tactics to access the image-centric social network service include using virtual private network software that encrypts and conceals online activity, said Meta head of security policy Nathaniel Gleicher.

People in Iran are also using a "light" version of the Instagram app released in Iran last year that is designed for places where internet bandwidth is meager, Gleicher added.

Meta has also put policies in place to remove posts that "outs" activists, journalists.

"It's an unfortunate reality that when a government wants to prevent its citizens from having access to public debate, they have a lot of tools in place that they can use to do that," Gleicher said during the briefing.

"But, we are seeing the Iranian efforts not be as effective as I'm sure they would like."

Since Amini's death, hashtags related to protests in Iran have been used on Instagram more than 160 million times, according to Meta.

Iran imposed sanctions this week on 36 individuals and entities from the European Union and Britain in reaction to similar measures against Tehran over its response to the protests.