(Reuters) - Facebook Inc and Twitter Inc said on Monday they had dismantled a state-backed information operation originating in mainland China that sought to undermine protests in Hong Kong.

FILE PHOTO: Stickers bearing the Facebook logo are pictured at Facebook Inc's F8 developers conference in San Jose, California, U.S., April 30, 2019. REUTERS/Stephen Lam

Social media companies are under intense pressure to stop illicit political influence campaigns online ahead of the U.S. presidential election in November 2020.

Here is a list of takedowns announced by Facebook so far this year:

** Jan. 17 - 364 Facebook pages and accounts operated from Russia and targeting the Baltics, Central Asia, the Caucasus, and Central and Eastern European countries.

** Jan. 31 - 783 pages, groups and accounts engaged in “coordinated inauthentic behavior tied to Iran.” 234 accounts, pages and groups on Facebook and Instagram operating as part of a domestic network in Indonesia.

** Feb. 13 - 168 Facebook accounts, 28 pages and eight Instagram accounts targeting people in Moldova. “Although the people behind this activity attempted to conceal their identities, our manual review found that some of this activity was linked to employees of the Moldovan government.”

** March 7 - 137 Facebook and Instagram accounts, pages and groups operating as part of a domestic-focused network in Britain. 31 Facebook pages, groups, and accounts which were part of a network that operated in Romania.

** March 26 - 2,632 pages, groups and accounts engaged in coordinated inauthentic behavior on Facebook and Instagram. The operations identified were connected to Iran, Russia, Macedonia and Kosovo.

** March 28 - 200 pages, groups and accounts engaged in coordinated inauthentic behavior on Facebook and Instagram in the Philippines.

** April 1 - 1,126 pages, groups and accounts linked to people and organisations in Pakistan and India. “The operations ... engaged in coordinated inauthentic behavior were two distinct sets of activity in India and one network in Pakistan.”

** May 6 - 97 Facebook accounts, pages and groups involved in coordinated inauthentic behavior as part of a network emanating from Russia that focused on Ukraine.

** May 16 - 265 Facebook and Instagram accounts, pages, groups and events which originated in Israel. The network targeted people in Nigeria, Senegal, Togo, Angola, Niger and Tunisia, along with some activity in Latin America and Southeast Asia.

** May 28 - 97 Facebook and Instagram accounts, pages and groups which originated in Iran. The accounts purported to be located in the U.S. and Europe and impersonated legitimate news organizations in the Middle East.

** July 25 - Four unconnected operations that originated in Thailand, Russia, Ukraine and Honduras. “We didn’t find any links between the campaigns we’ve removed, but all created networks of accounts to mislead others about who they were and what they were doing.”

** Aug. 1 - 383 accounts, pages and groups on Facebook and Instagram linked to marketing firms in the UAE and Egypt. 397 accounts, pages and groups on Facebook and Instagram linked “to individuals associated with the government of Saudi Arabia.”

** Aug. 19 - Facebook removes a network of 15 pages, groups and accounts to stop what it says appears to be a state-backed information operation originating in mainland China that sought to undermine protests in Hong Kong. Twitter suspends over 200,000 accounts.