Dubai - Envoys in Dubai signed a new UN telecommunications treaty on Friday that a US-led delegation says endorses greater government control of the internet. The US and more than 20 other countries refused to ratify the accord by the 193-nation International Telecommunications Union.Here is a look at internet restrictions and availability at selected countries and regions around the world:- North KoreaInternet use is extremely restricted with many of North Korea's 24 million people unable to get online. Some North Koreans can access an internal intranet that connects to state media. Members of the elite, resident foreigners and visitors in certain hotels are allowed full access to the internet.- IranMost Western social media sites such as Facebook and Twitter are blocked in Iran, as well as political opposition and sexually explicit websites. But proxy server sites and other methods are widely used to get around the official restrictions. Iran has announced plans to create its own domestic internet with fully monitored content, but international experts question whether such a complete break from the worldwide web is possible. Earlier this week, Iran accounted it had developed its own YouTube-style video sharing site.- ChinaThere are more than 500 million Chinese online but they contend with an extensive internet filtering and censorship system popularly known as the "Great Fire Wall". Censors police blogs and domestic social media for content deemed pornographic or politically subversive and delete it. Many foreign websites, including YouTube, Facebook, Twitter and the New York Times are blocked. Searches for controversial topics such as corruption scandals or jailed Nobel Peace Prize winner Liu Xiaobo return error messages. Users evade controls using proxy servers.- CubaTight control, slow connections and high costs mean only around 5% of Cubans have access to the global internet, with another 23% relying instead on a government intranet with very limited content. Web access is mainly via public facilities where people must first register with identification.- Gulf Arab StatesPolitical sites deemed threats to the state are often blocked. Since the Arab Spring, authorities across the Gulf have stepped up arrests of bloggers and others for posted considered offensive to rulers or advocating political reforms.- Central AsiaInternet censorship is prevalent across former Soviet Central Asian republics, but the strongest restrictions have been recorded in Iran's authoritarian neighbours to the north, Turkmenistan and Uzbekistan. Controls are strictest in Turkmenistan, where social networking sites Facebook and Twitter are out-of-bounds, as is video-sharing site YouTube and numerous news websites. Uzbekistan has taken a less extreme approach, but sites critical of the government are blocked as a matter of course. Tajikistan, which is like those countries also ruled by an unchallenged strong-man ruler, has twice this year barred access to Facebook after web-surfers used the site to post material critical of government officials.