WASHINGTON — Social media companies such as Facebook and Twitter need to be more aggressive in monitoring and taking down hate speech that can incite violence, Sen. Mark Warner, D-Virginia, said Tuesday.

“Frankly, social media has been very slow to respond,” said Warner, the vice chairman of the Senate Intelligence Committee, who has been putting pressure on companies to develop guidelines that can help curb hateful posts and commentary online.

While there has been a lot of support for family and friends of the 11 victims shot and killed at a synagogue in Pittsburgh Saturday, there has also been a torrent of anti-Semitic remarks on the web.

A New York Times search of Instagram posts for the word “Jews” on Monday found 11,696 posts with the hashtag “#jewsdid911,” referring to a claim that Jews were behind the Sept. 11 terror attacks.

“I think there needs to be at least some ‘decency doctrine’ that would put some guardrails” on hate speech, Warner said while discussing the shooting and the recent pipe bomb threats made against prominent Democrats, including former Vice President Joe Biden and former Secretary of State Hillary Clinton, as well as members of Congress.

“If you’re on a responsible website, I think some notion around hate speech, particularly when you see the kind of violence that it incites — this needs to be dealt with,” Warner said.

Warner has encouraged social media companies to work with Congress as lawmakers press for more transparency in how the firms operate. The Senate intelligence panel held a hearing in September on dealing with foreign threats, which included testimony from high-ranking officials from Facebook and Twitter. Warner was disappointed by Google’s decision not to send anyone.

Facebook and Twitter have said they’ve put more resources into identifying hateful posts, bogus accounts and automated bots. Earlier this month, Twitter said it will display a notice when a tweet is taken down because it violated Twitter rules. And Facebook recently showed off its election “war room,” where the social network has set up a team to deal with fake accounts and disinformation ahead of next week’s midterm elections.

Warner said he intends to keep up pressure on social media companies to take more responsibility for their platforms and the content posted by hundreds of millions of users.

“The companies have to be willing to step forward,” Warner said. “In many ways, I think they hope that government and regulators will simply go away. We’re not going away.”

Earlier this year, Warner released a white paper which included a list of possible policy proposals for regulation of social media and technology firms.