Social media like Facebook and Twitter have become important elements in political and social discourse in a number of countries, particularly in the Arab world, a survey showed.

A 21-nation survey found wide use of social networks across the globe, and that many people, especially in Arab countries, are using these networks to express social and political views.

"Expressing opinions about politics, community issues and religion is particularly common in the Arab world," said the Pew Research Center's Global Attitudes Project survey.

"For instance, in Egypt and Tunisia, two nations at the heart of the Arab Spring, more than six in 10 social networkers share their views about politics online."

That compared with about a third of users overall in the survey, Pew said.

Among social network participants in Lebanon, for example, 68 percent said they shared views on politics and 81 percent on community issues. Similarly high levels were found in Tunisia, Egypt and Jordan.

The survey noted that social networking "has spread around the world with remarkable speed" in both advanced and developing countries.

It found that younger people were leading the way in the use of social networks, and that smartphones were being used widely to connect.

"Globally, most smartphone users say they visit social networking sites on their phone, while many get job, consumer, and political information," Pew said.

"Technologies like these are especially popular among the young and well educated. In almost every country polled, people under age 30 and those with a college education are more likely to engage in social networking and to use a smartphone."

Roughly half of the people surveyed in the United States, Britain, Russia, Spain and the Czech Republic said they used social networks, as did around four in 10 in Poland, Brazil, France and Italy.

In most of the other nations surveyed, around one-third said they used social networks, but the figure was just six percent in India and three percent in Pakistan.

"There is considerable interest in social networking in low- and middle-income nations," said the report.

"Once people in these countries are online, they generally become involved in social networks at high rates. For instance, the vast majority of Internet users in Mexico, Brazil, Tunisia, Jordan, Egypt, Turkey, Russia and India are using social networking sites."

The exceptions were in Japan and Germany, the only two countries where fewer than half of all Internet users participate in social networks, the survey found.

In all countries, those in the 18-29 age group were the heaviest users of social networks, with more than 90 percent participating in several countries. Those in the 30-49 age category were generally more active than their peers over 50.

Among those who participate in social networks, commenting on music and movies is a popular activity, with majorities in 17 countries saying they have done this.

In China, 86 percent said they shared views about music and movies on social networks, as did 85 percent in India, 84 percent in Mexico, 83 percent in Greece and 78 percent in Turkey.

Sports, on the other hand, was a less common topic, with half or more of users of social networks in only seven countries -- India, Jordan, Tunisia, Turkey, Egypt, Brazil and China -- saying they have shared opinions on sports.

The report was based on a survey of more than 26,000 people in the 21 countries in March and April 2012.