A 10-year-old boy looks at an online video in Berlin, on January 26, 2011. Australian children are accessing social media websites at an increasingly younger age, a new survey suggests, with one in five "tweens" admitting they have chatted to someone online they do not know.

Australian children are accessing social media websites at an increasingly younger age, a new survey suggests, with one in five "tweens" admitting they have chatted to someone online they do not know.

The report "Tweens, Teens and Technology" by online security company found that children in the tweens age category of eight to 12 were adopting technology faster than expected, with 67 percent using a social media website.

Despite the age eligibility for Facebook being 13, one in four (26 percent) admitted to using the site—although 95 percent said they had their parents' permission to do so.

The most popular site for tweens was Skype (used by 28 percent), but children were also using Instagram, according to the survey of 500 geographically representative of Australia's online .

While the survey found that one in five tweens (19 percent) said they chatted to someone online that they did not know, only seven percent said they had shared personal information.

Australia's Communications Minister Stephen Conroy said it was troubling that children talk to strangers online.

"It shows we must remain vigilant to online threats," he said.

The findings suggest the age at which children first use social media is falling, given a 2012 McAfee survey of teens aged 13-17 found the average age they opened their first social network account was 13.

On average, tweens were using three or four devices that can be Internet enabled, with 66 percent opting for mobile phones and/or tablets. Fifty-four percent said they used a tablet for more than an hour a day.

Most use their devices to access the Internet, and on average spend about 1.5 hours a day accessing the web, the survey said.

"Both parents and schools are encouraged to keep a close monitor on their child's online behaviour to ensure they have safe online ," said Andrew Littleproud, president of McAfee Asia-Pacific.

"By working closely with child psychologists, we have seen that online behaviours become entrenched in the tween age group so proactive education is critical within eight to 12 age bracket."