The diplomatic world is considered to be one of protocol and discretion, yet an increasing number of foreign policy officials and diplomats are conducting their business in the most public way possible, on Twitter.

On the morning that Ratko Mladic appeared before the UN war crimes tribunal, the British Foreign Secretary William Hague took to Twitter to issue the kind of diplomatic broadside of which his predecessor, Viscount Palmerston, would have been proud.

"Syrian leaders should reflect on the sight of Mladic in the dock today - reach of international justice is long."

Palmerston, the 19th Century British statesman who served both as foreign secretary and prime minister, was famed for his gunboat diplomacy. Hague, a prolific tweeter, was practising a 21st Century variant: e-diplomacy.

Like Hague, Carl Bildt, Sweden's foreign minister, is also fluent in this new diplomatic tongue. During the government crackdown on demonstrations in Bahrain last year, he took to the Twittersphere to berate his Bahraini counterpart: "@khalidalkhalifa Trying to get in touch with you on an issue"

With its 140-character limit, Twitter hardly lends itself to diplomatic nuance. But its abbreviated form, in harness with its hashtag hieroglyphics, can also make it powerfully direct.

The popular social media site is just one of the online tools that governments are increasingly using to extend their spheres of internet influence. The web can help deliver consular advice, explain policy, and reach and engage with new audiences. It can also be used to issue admonishments and warnings and, on occasions, help solve problems.

US State Department Employs more than 150 people to deal with social media

Has developed its own internal version of Facebook and Wikipedia

Advises people how to circumvent government censorship

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.

A recent training session at the headquarters in Foggy Bottom even saw a classroom full of diplomats being schooled in social media techniques by a 20-something intern. The advice: "Go ahead and give it a go." Already more than 900 diplomats at US missions around the world have heeded that advice, and are using social media as part of their day-to-day diplomacy.

Fergus Hanson, from the Lowy Institute in Sydney and an expert in e-diplomacy, eavesdropped on that Foggy Bottom session. "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 US thinks internet freedom will be a defining issue of the century Fergus Hanson, Lowy Institute, Sydney

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.

The State Department also uses a form of crowdsourcing to come up with solutions to problems. For instance, it went online to ask its employees for cost-cutting ideas. A diplomat in China, who suspected that electricity was being stolen from the US embassy compound by nearby residents tapping into a wire, proposed setting up a meter to chart its usage. It not only showed that neighbours were stealing electricity, but that the energy company was overcharging. The discovery saved tens of thousands of dollars.

In its public diplomacy, the State Department has taken to the web to advise on how people can circumvent restrictive firewalls and beat online government censorship.

"The US thinks internet freedom will be one of the defining issues of this century," says Hanson. Indeed, the fight between an open and closed internet has been likened to the Cold War fight between capitalism and communism. Here, Washington has not only been critical of China. It raised objections to Australia's plans to introduce an internet filter, and was not impressed when David Cameron raised the possibility of shutting down social networking sites during situations like the 2011 London riots.

Image caption Russia is waking up to Twitter's potential

Since publishing a landmark study on e-diplomacy in March this year , Hanson has been contacted by countries such as China and Russia who are looking to benefit from his expertise. Smaller nations, like Ireland and New Zealand, are also looking at the potential of e-diplomacy, partly because it is so inexpensive and can help overcome the problem of geographic remoteness.

For the British Foreign and Commonwealth Office, blogging has been useful in shedding its famously stuffy image. Recently, Paul Madden, the High Commissioner in Canberra, informed readers on his blog that he had seen Scotland win its first rugby match on Australian soil for 30 years .

Greg Dorey, the ambassador to Ethiopia, reported on the country's largest private equity investment to date: a brewery . "Today was about beer," he wrote. "And as Benjamin Franklin put it, 'beer is proof that God loves us and wants us to be happy.'"

But most e-diplomacy is far more serious. Peter Millett, the ambassador to Jordan, used his blog to describe a recent scene at the Syrian border : "The man was clearly traumatised after crossing the border from Syria. His eyes wide, he told us that he had seen his sister and her seven children murdered by regime thugs."

Some foreign ministers have gone for a very chatty style of tweeting.

As well as chronicling his diplomatic travels, Bob Carr, Australia's new foreign affairs minister, has been known to inform his 15,000 followers what he has just had for dinner. Recently, it was tender kangaroo cooked over a bed of fresh tomatoes, ginger, herbs, fennel, brussels sprouts and herbs, which he judged to be "terrific."

He also links to his personal blog, Thoughtlines , which offers film and book reviews. Kevin Rudd, Carr's predecessor as foreign affairs minister, tweeted about the health of his cat, Jasper. The Australian Department of Foreign Affairs and Trade, however, has been slow to grasp the potential of e-diplomacy. It maintains just one twitter feed, and has been reluctant to unleash its diplomats on the blogosphere.

Image caption Just like the rest of the world, diplomats tweet about their dinner

E-diplomacy certainly carries risks. Even experienced practitioners, like the Swedish foreign minister Carl Bildt, have run into trouble. Ahead of this year's World Economic Forum in Davos, he drew criticism for what many thought was an insensitive missive: "Leaving Stockholm and heading for Davos. Looking forward to World Food Program dinner tonight. Global hunger is an urgent issue! #davos."

Hunger and a slap-up meal did not sit happily side by side. In the argot of the Ttwittersphere, the tweet was judged a #fail.

Some prefer to maintain a diplomatic silence. Hillary Clinton, despite investing heavily in harnessing the power of the internet, does not tweet.

But e-diplomacy is the talk of foreign ministries the world over, as foreign affairs is increasingly conducted in 140 characters or less.