Two people have already been arrested by police in this connection.
A man has been arrested in Bristol after sending threatening messages through Twitter.
The 32-year-old is suspected to have sent a barrage of threatening tweets against Labour MP Stella Creasy and feminist campaigner Caroline Criado-Perez.
The Central eCrime Unit of MPS Police arrested the person under the Protection of Harassment Act, 1997, after tracing him to a Bristol address.
Walthamstow MP Stella Creasy and Caroline Criado-Perez, who successfully campaigned for a woman’s face to appear on £10 banknotes, had complained of the abusive tweets on 25 and 29 July.
Two others have already been arrested by police.
A Scotland Yard spokesman said: "He was arrested at an address in Bristol by officers from the MPS (Metropolitan Police Service) Police Central eCrime Unit as part of an ongoing investigation into allegations relating to threats made on Twitter."
"The man will be taken to a Bristol police station," the spokesperson added.
"He has been arrested in connection with allegations made to police by two women, who made reports to police on July 25 and 29."