Domestic governments and local actors engaged in online interference in efforts to influence 26 of 30 national elections studied by a democracy watchdog over the past year, according to a report released on Monday.
Freedom House, which is partly funded by the US government, said that internet-based election interference has become "an essential strategy" for those seeking to disrupt democracy.
Disinformation and propaganda were the most popular tools used, the group said in its annual report. Domestic state and partisan actors used online networks to spread conspiracy theories and misleading memes, often working in tandem with government-friendly media personalities and business figures, it said.
"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."
Some of those seeking to manipulate elections had evolved tactics to beat technology companies' efforts to combat false and misleading news, the report said.
In the Philippines, for example, it said candidates paid social media "micro-influencers" to promote their campaigns on Facebook Inc, Twitter Inc and Instagram, where they peppered political endorsements among popular culture content.
Online disinformation was prevalent in the United States around major political events, such as the November 2018 midterm elections and the confirmation hearing for Supreme Court nominee Brett Kavanaugh, the report said.
Freedom House also found a rise in the number of governments enlisting bots and fake accounts to surreptitiously shape online opinions and harass opponents, with such behaviour found in 38 of the 65 countries covered in the report.
Social media was also being increasingly used for mass surveillance, with authorities in at least 40 countries instituting advanced social media monitoring programs.
China was ranked as the world's worst abuser of internet freedom for a fourth consecutive year after it enhanced information controls in the face of anti-government protests in Hong Kong and ahead of the 30th anniversary of Tiananmen Square.
For instance, Beijing blocked individual accounts on WeChat for "deviant" behaviour, which encouraged self-censorship, the report said.
The Philippine and Chinese embassies in Washington, DC, did not immediately respond to requests for comment outside of normal business hours.