Twitter has apologised to a group of high-profile women in the UK who have been threatened with death and rape on the site.
It also announced measures to make it easier for users to report abusive tweets.
The micro-blogging site had come under increasing pressure to react after a feminist campaigner, several women members of parliament and journalists were targeted by users who hurled misogynistic abuse at them and in some cases made violent threats.
"I personally apologise to the women who have experienced abuse on Twitter and for what they have gone through," Tony Wang, general manager of Twitter UK, said on his own Twitter feed.
"The abuse they've received is simply not acceptable. It's not acceptable in the real world, and it's not acceptable on Twitter," he said.
Twitter UK said it was adding staff to help handle abuse reports. It also said an in-tweet "report abuse" button currently available on the Twitter app for iPhones would be added to the Twitter website and to platforms used on other mobile devices.
The problem of abuse by so-called internet "trolls" was highlighted after activist Caroline Criado-Perez was hit by a barrage of vitriolic tweets after successfully campaigning for a woman's face to appear on sterling bank notes.
In recognition of her role, Ms Criado-Perez appeared alongside Bank of England Governor Mark Carney on 24 July, when he announced 19th century novelist Jane Austen would become the face of the new £10 note.
Police arrested two men over rape threats against Ms Criado-Perez..
One of them was also suspected of making rape threats against opposition Labour legislator Stella Creasy, who backed the bank note campaign and also appeared with Mr Carney.
In separate incidents days later, several high-profile female journalists received tweets from someone threatening to bomb their homes and "destroy everything" there.
London's Metropolitan Police Service said yesterday it was investigating allegations made by eight people who have been subjected to harassment, malicious communication or bomb threats.
While the trolls themselves have been denounced across British media, Twitter had also come under heavy criticism for its failure to respond forcefully enough.
In a statement issued after Mr Wang's apology, Ms Criado-Perez welcomed the new measures but said a more profound overhaul of the social network's system for handling abuse was needed.
"The current process is lengthy, complicated and impossible to use if you're under sustained attack like I have been," she said.
"Right now, all the emphasis is on the victim, often under intense pressure, to report rather than for Twitter to track down the perpetrator and stop them."