The current Turkish block on Twitter is the latest in a series of actions against social networks, which often happen when a government's grip on power is under threat. Here are some other examples.
EGYPT (January 2011): Setting a historic precedent, Egyptian authorities blocked Internet access on January 28, 2011, to undermine opponents to the regime of president Hosni Mubarak who had used Facebook and Twitter to organise rallies.
The shutdown lasted five days and affected 23 million Egyptians with regular or occasional access to the Internet, according to official figures, more than a quarter of the population.
IRAN (since June 2009): Authorities have blocked access to Twitter, Facebook and other social networks used by the opposition since the disputed re-election of former Iranian president Mahmoud Ahmadinejad in 2009.
Although there are 34 million Internet users in Iran, almost half of the country's 75 million-strong population, the government tries regularly to control the web, such as by blocking access to opposition websites or those with sexual content.
Since being elected in June 2013, President Hassan Rouhani has eased some social and political restrictions.
MYANMAR (late September 2007): Web access was cut for several days during the "Saffron Revolution", when Buddhist monks protested against the ruling military junta.
A Myanmar telecoms official blamed a damaged undersea cable, but a reliable Western source said it was a deliberate act by officials aimed at disrupting the distribution of images and information on a crackdown.
Today, Internet connections are also subject to cuts in service on certain dates, such as August 8, the anniversary of a 1988 revolt. Control of the web is also tighter during election campaigns.
ELSEWHERE: The Internet is subject to strict censorship in China, where Twitter and Facebook are banned and where the authorities try to prevent access to images or comments on domestic sites related to the July 2009 riots in the western province of Xinjiang.
In Syria, scene of an ongoing three-year civil war, social networks were cut for three days in November 2012 in several regions including the capital Damascus. The official Sana news agency said that was due to maintenance work.