Australia's online watchdog said Monday it has fined Telegram more than $600,000 for missing a deadline to reveal how it tackles "terrorist" and child sexual abuse content.

The encrypted messaging firm replied more than five months after the May 6, 2024 limit for disclosing its online safety compliance, eSafety Commissioner Julie Inman Grant said.

In March last year, the watchdog asked Telegram and other platforms what they were doing to detect "terrorist," violent extremist, and child sexual exploitation content, she said in a statement.

Telegram did not reply until Oct. 13, obstructing the commission's work for almost half a year, she said.

"Surfacing how and where some of these platforms might be failing ― and also succeeding ― in tackling this content is vital to protect the community and raise safety standards across the industry, especially where this most abhorrent of content is concerned."

Telegram, which was fined Aus$958,000 ($613,000), has 28 days to pay the penalty, seek more time to pay, or try to get it withdrawn.

If it decides not to pay, the commission can seek a penalty in the federal court.

Telegram's Russian-born founder and chief executive Pavel Durov was arrested in August last year at a Paris airport and later charged with several counts of failing to curb extremist and terrorist content on the app.

French prosecutors also claimed the Dubai-based platform had failed to take action against child sexual abuse imagery.

Durov, who was released on a five-million-euro (US$5.3 million) bail, later announced a crackdown on illegal content.