Facebook and Twitter say they have removed numerous false social media accountslinked to Russia that targeted the American public.Facebook said in a statement that the network of accountsappeared to be in the process of building up a following of U.S.-based users.The network was operated by people in Ghana and Nigeria for individuals in Russia.Facebook said its investigation found that the accounts had ties to individualslinked to past activity by Russia's Internet Research Agency.U.S. officials have accused that group of leading a major disinformation campaign onlinein an attempt to influence the 2016 U.S. presidential election.In some cases, the removed accounts claimed to be nongovernmental organizations or personal blogs.The accounts on Facebook and on the company's Instagram service attempted to gain usersby posting about issues like black history, fashion, and news about famous Americans.In total, Facebook removed 49 accounts, 69 Facebook pages and 85 Instagram accounts.Twitter removed 71 accounts.Facebook said the accounts did not appear to center on elections.They also did not include support or criticism of individual political candidates.Facebook's statement said that while the company is making progress in identifying and stopping such abuses,the problem represents "an ongoing challenge" it is dealing with."That means building better technology, hiring more people and working more closely with law enforcement,security experts and other companies," the statement said.Twitter said the accounts it removed dealt mainly with social issues such as race and civil rights,without favoring any candidate or political ideas.The latest removals follow a recent report that found Russia's campaign of election interferencehas not reduced since 2016 -- and appears to be getting more difficult to discover.Young Mie Kim, a professor at the University of Wisconsin-Madison created the recent report.She found that Russia-linked social media accounts were posting about many of the same issues as during the 2016 elections.These include race relations, gun laws and immigration.Facebook has since removed those accounts, too.Last month, the director of the Federal Bureau of Investigation, Christopher Wray,warned that Russia was still involved in a campaign of "information warfare"that uses false social media accounts to spread disinformation.Russia has repeatedly denied interfering in U.S. elections.