The increasing use of social media by governments to manipulate elections and monitor citizens has resulted in a decline in global internet freedom for a ninth consecutive year, according to an annual assessment by the Washington, D.C., think tank Freedom House.

The "Freedom on the Net 2019" report found that governments in 26 countries manipulated national elections over the past year through tactics such as disinformation, blocking websites and cutting off access to the internet.

"Many governments are finding that on social media, propaganda works better than censorship," said Mike Abramowitz, president of Freedom House. "Authoritarians and populists around the globe are exploiting both human nature and computer algorithms to conquer the ballot box, running roughshod over rules designed to ensure free and fair elections."

"Freedom on the Net 2019" assesses internet freedom in 65 countries that account for 87 percent of internet users worldwide.

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Freedom House said it has found evidence of advanced social media surveillance programs in at least 40 of the countries analyzed.

Governments are indiscriminately monitoring citizens' online behavior to identify perceived threats and in some cases to silence opposition, the think tank said.

"Once reserved for the world’s most powerful intelligence agencies, big-data spying tools are making their way around the world," said Adrian Shahbaz, Freedom House's research director for technology and democracy. "Advances in AI are driving a booming, unregulated market for social media surveillance. Even in countries with considerable safeguards for fundamental freedoms, there are already reports of abuse."

Freedom House said that of the 65 countries assessed in its report, a record 47 featured arrests of users for political, social or religious speech.

"The future of internet freedom rests on our ability to fix social media," said Shahbaz. "Since these are mainly American platforms, the United States must be a leader in promoting transparency and accountability in the digital age. This is the only way to stop the internet from becoming a Trojan horse for tyranny and oppression."