(Reuters) - Twitter Inc TWTR.N plans to toughen its rules on online sexual harassment and impose stronger penalties for misconduct, according to an email it sent to a group of safety advocates, academics and researchers that helps the social media service set its policies.

The new rules, which will likely be introduced in the next few weeks, are aimed at tackling one of Twitter’s biggest and long-lasting problems. They follow a series of tweets by Chief Executive Jack Dorsey on Friday announcing plans to act more aggressively to limit the number of bullies and harassers using Twitter.

The new guidelines include immediate and permanent suspensions of any account Twitter identifies as the original poster or source of non-consensual nudity. The site’s definition of non-consensual nudity will also be expanded to include what it called “upskirt imagery, creep shots and hidden camera content.”

The rules were set out in a letter, which was seen by Reuters, to Twitter’s Trust and Safety Council from Twitter’s head of safety policy.

The micro-blogging platform is also looking to allow bystanders to report unwanted sexual advances, which previously had to be reported by users directly involved in the situation.

It also promised to publish more details on a change in policy which would include hate symbols and imagery in its definition of sensitive media.

Dorsey’s pledge to revamp Twitter’s guidelines came after some users boycotted the service for suspending actress Rose McGowan, who spoke out against Harvey Weinstein, the producer who faces allegations that he sexually harassed or assaulted a number of women over three decades in the film business. Weinstein has denied having non-consensual sex with anyone.

Twitter also faces scrutiny from lawmakers investigating allegations of Russian interference in the 2016 U.S. presidential election.

Last week, Twitter gave Senate investigators the profile names of 201 accounts it had determined were linked to an effort by Moscow to sow discord and divisiveness during and after the campaign, according to a source familiar with the matter.

Senator Mark Warner, the top Democrat on the Senate Intelligence Committee investigating Russian interference, previously called Twitter’s cooperation as “frankly inadequate.”