The British Transport Police (BTP) said on Wednesday that a woman in her 30s from Northampton has been arrested in connection with a hate crime which took place at London Victoria station on Saturday.
The force added that she is currently in police custody.
Meanwhile, a fourth person has been arrested in connection with a racially aggravated altercation which took place at London Waterloo Station on the same day.
The other three, all men, were arrested after racist abuse was shouted at pro-Palestine protesters at Waterloo.
In an earlier statement, BTP said the three men were detained “in connection with a racially aggravated altercation” after the protest was dispersed at around 5.30pm on Saturday.
They included a 57-year old from Surbiton, south west London; a 61-year old from West Molesey, Surrey; and a 33-year old from Christchurch, Dorset.
The Metropolitan Police said 126 people were arrested during the Armistice Day protests and counter-protests.
So far 11 people have been charged with offences including assault on an emergency worker, criminal damage, racially aggravated assault and possession of an offensive weapon.
The force added that 18 officers were injured policing the protests.