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Twitter said on Thursday it had suspended hundreds of Russian-linked accounts and would ramp up enforcement of its spam rules as it probes online campaigns to influence the 2016 U.S. election.

Although the company’s disclosures in briefings to U.S. congressional staff and a public blog post were its most detailed to date on the issue, Senator Mark Warner, the top Democrat on the Senate Intelligence Committee, called the company’s statements “deeply disappointing.”

Twitter said it would toughen restrictions on suspect spammers, for example by reducing the time that suspicious accounts stay visible during company investigations.

Twitter allows fictitious names and some automation by accounts, making it harder to distinguish improper activity.

Figures in the company’s blog showed the scale of the issue. In battling the automated promotion of trending topics, which get displayed to many users, the company said it counteracted 130,000 accounts daily.

To thwart abuse via applications interacting with Twitter, the company said it had suspended 117,000 apps since June that had been responsible for 1.5 billion “low-quality” tweets this year.

Twitter said it wanted to work more closely with election and other officials and wanted to strengthen disclosures on optical advertising, as Facebook has just done.

Warner is leading efforts to introduce legislation requiring internet platforms to reveal who is purchasing online political ads, which would bring them in line with rules governing ads on radio or television.

Colin Crowell, Twitter’s vice president of public policy, was among company representatives who met behind closed doors with Senate Intelligence Committee aides on Thursday.