Shares of Facebook Inc. and Twitter Inc. fell on Wednesday as their top executives testified before the U.S. Congress, defending the companies against what lawmakers see as a failure to combat continuing foreign efforts to influence U.S. politics.

Facebook (FB.O) fell 1.6 percent and Twitter (TWTR.N) 5.2 percent. Shares of other tech companies, including Alphabet (GOOGL.O) and Snap (SNAP.N), were also down.

"Twitter does not have the broad number of revenue drivers that Facebook has as far as messenger and Instagram, nor does it have the development infrastructure for new applications the way Facebook does, so that's why it is selling off more," Tigress Financial Partners analyst Ivan Feinseth said.

Twitter Chief Executive Officer Jack Dorsey said in his prepared remarks that a "relatively small number of bad-faith actors were able to game Twitter to have an outsized impact."

Facebook Chief Operating Officer Sheryl Sandberg acknowledged to the Senate Intelligence Committee that the company was too slow to respond to Russian efforts to interfere in the 2016 U.S. election and general American political discourse, but insisted it is doing better.

Prior to the hearing, President Donald Trump in an interview with the Daily Caller accused social media companies of interfering in the U.S. mid-term elections in November, without appearing to offer any evidence.