US President Barack Obama has signed a secret order authorising US support for rebels seeking to depose Syrian President Bashar al-Assad and his government, Reuters news agency said quoting sources familiar with the matter.

The White House has apparently stopped short of giving the rebels lethal weapons, even as some US allies have been doing just that.

A US government source acknowledged that under provisions of the presidential finding, the US was collaborating with a secret command centre operated by Turkey and its allies.

The acknowledged leader in this field is the US State Department, which now boasts more than 150 full-time social media employees working across 25 different offices. It uses familiar sites like YouTube, Facebook and Twitter, as well as local equivalents, such as VKontakte in Russia. Ambassadors and other State Department employees are encouraged to establish an online presence.

"The State Department is really creating what is effectively a media empire that could soon be the digital equivalent of old school international broadcasters like the BBC," he says. "But they not only see it as part of a broadcasting strategy, they are looking at the wider potential." Social media acts like an early warning system of emerging social and political movements, he says. It is also a way of reaching online opinion formers, and a means of correcting misinformation very quickly.

The State Department now has an internal version of Wikipedia called Diplopedia, which has more than 14,000 entries. To encourage internal networking, there is also an equivalent of Facebook called Corridor - in the look and feel, the two are strikingly similar - which has over 6,500 members.

In a reference to Russia's ambitions in the Arctic, where Moscow plans to expand its claims, Putin said the navy would protect Moscow's interests in the icy North."Obviously, the navy is an instrument to protect national economic interests, including in such regions as Arctic where some of the world's richest biological resources, mineral resources are concentrated," he said.

Moscow has planned to submit a claim this year to redraw the map of the Arctic and give itself a bigger swath of the territory, which could hold huge deposits of oil, gas and mineral wealth.Russia, Norway, the United States, Canada and Denmark are at odds over how to divide up the Arctic seabed, thought to hold 90 billion barrels of oil and 30 percent of the world's untapped gas resources, according to the U.S. Geological Survey.