Facebook is preparing to launch a new feature for its Messenger app which allows users of the social networking site to place free voice calls tofriends.

The feature is so far available only to smartphone users in Canada and is buried within the latest update to the app, but it will eventually allow users to make free internet voice calls, known as VoIP calls, to any Facebook friend.

Experts are saying it represents an attempt by the world's largest social network to dominate the social world by taking on the default calling function in mobile phones, the 'Daily Mail' reported.

The new feature comes at the same time as Facebook Messenger rolled out a new feature worldwide which allows users to record and send a voicemail-type message to friends.

Working in a similar way to video messaging in the company's Poke app, users press and hold a red record button, speak their message, and it appears in line as part of the conversation.

TechCrunch writer Josh Constine imagines a range of uses for the function, from messaging while driving to recording the waves lapping at a beach to send to friends.

However, its addition to the Messenger app seems merely to make it an 'even more complete app' he writes, adding that he expects video messaging to soon be added as well.

One-tenth the size of the US, but with very similar demographics and mobile usage trends, Facebook is using Canada as a testing ground in advance of rolling out the feature in other markets, the paper said.

By clicking the 'i' icon in the top right of a conversation in the most recent update to Messenger, users reveal a 'free call' button which allows them to contact any friend also within the test region.

However, while Facebook is not charging users for the service, the call is not technically free since it will use data on users' existing mobile plans.

TechCrunch said that the move into voice messaging and VoIP can be seen as an attempt by the social network to take on the default, mobile network operated calling function on smartphones.

 Internet and other components of information communication and technology (ICT) industry annually produces more than 830 million tonnes of carbon dioxide (CO2), the main greenhouse gas, and is expected to double by 2020, a new study has found.

Researchers from the Centre for Energy-Efficient Telecommunications (CEET) and Bell Labs explain that the information communications and technology (ICT) industry, which delivers Internet, video, voice and other cloud services, produces about 2 per cent of globalCO2 emissions -- the same proportion as the aviation industry produces.

In the report published in journal Environmental Science & Technology, researchers said their projections suggest that ICT sector's share in greenhouse gas emission is expected to double by 2020.

They have also found new models of emissions and energy consumption that could help reduce their carbon footprint.

The study said that controlling those emissions requires more accurate but still feasible models, which take into account the data traffic, energy use and CO2 production in networks and other elements of the ICT industry.

Existing assessment models are inaccurate, so they set out to develop new approaches that better account for variations in equipment and other factors in the ICT industry.

They describe development and testing of two new models that better estimate the energy consumption and CO2 emissions of Internet and telecommunications services.

The researchers suggest, based on their models, that more efficient power usage of facilities, more efficient use of energy-efficient equipment and renewable energy sources are three keys to reducing ICT emissions of CO2.