The National Association for the Advancement of Colored People, one of the oldest U.S. civil-rights organizations, has returned a donation it received from Facebook Inc. (FB.O) and is encouraging a week-long boycott starting Tuesday, Dec. 18.

The NAACP urged its members and supporters to log out of Facebook and sister site Instagram in response to a report released Monday which found that Russian hacking of the 2016 election heavily targeted African-Americans.

"Facebook’s engagement with partisan firms, its targeting of political opponents, the spread of misinformation and the utilization of Facebook for propaganda promoting disingenuous portrayals of the African American community is reprehensible," NAACP president and CEO Derrick Johnson said in a statement.

The NAACP is also asking Congress to further investigate Facebook’s involvement in Russian hacking. In a tweet, the Congressional Black Caucus signaled its willingness, writing, "Last year we met with Facebook & other tech companies about this issue. If they can’t stop the weaponization of their platforms, then Congress will."

Facebook said in a statement that it has provided thousand of ads to lawmakers and made progress in preventing interference during elections.

African Americans have a strong presence on social media: 70 per cent of black U.S. adults use Facebook and 43 per cent use Instagram, the Pew Research Center has found. African Americans are more likely to use Facebook to communicate with family and friends daily, Pew’s research found. Sixty-three percent use Facebook to communicate with family, and 60 per cent use it to communicate with friends at least once a day, compared with 53 per cent and 54 per cent of the total population, respectively.