SYDNEY (Reuters) -Meta will block Australian users under 16 from accessing Instagram, Facebook and Threads by December 10 to comply with the country's sweeping social media ban for teenagers, the company said on Thursday.

The company said it had begun notifying users it believed were between 13 and 15 years old that their accounts will be shut down through in-app messages, email and texts. 

From December 4, it will start deactivating the accounts and blocking new sign-ups by anyone under 16.

Meta said the process was expected to be complete by December 10, after previously indicating to lawmakers it would only begin removing access once the law takes effect on that date.

It said it would use several age assurance methods to comply with the ban and adopt a "data minimisation approach", only seeking additional information when it had reason to doubt a user's stated age.

"While we are working hard to remove all users who we understand to be under the age of 16 by 10 December, compliance with the law will be an ongoing and multi-layered process," said Antigone Davis, vice president and global head of safety.

According to Australia's internet regulator, there are about 150,000 Facebook users aged between 13 and 15 in Australia, and 350,000 Instagram users. No data has been published for Threads.

Meta said affected teenagers can update their contact details to be notified once they turn 16, download their data or opt to delete their accounts.

Australia's social media ban is one of the most comprehensive efforts by a government to police minors' access to social media and is being closely watched by regulators around the world.

It puts the onus on social media platforms to take "reasonable steps" to block minors from having accounts. Platforms that breach the law could be fined up to A$49.5 million ($32.09 million).

($1 = 1.5427 Australian dollars)