More than 100 people have been arrested across the UK during protests in support of Palestine Action.
The group was banned as a terrorist organisation in June.
In Liverpool city centre, four people were arrested on suspicion of terrorism offences on Sunday afternoon, Merseyside Police said.
Material in support of the proscribed group was reportedly seen in the possession of a small number of protesters taking part in the regular march for Liverpool Friends of Palestine.
Four people from Merseyside – a 74-year-old woman from Kensington, a 65-year-old man from Brighton-le-Sands, a 28-year-old man from Garston and a 72-year-old man from Mossley Hill – were arrested on suspicion of wearing or carrying an article supporting a proscribed organisation, the force said.
All had been taken to police stations for questioning.
Protests were held in London, Manchester, Edinburgh, Bristol and Truro on Saturday as part of a campaign co-ordinated by Defend Our Juries.
The Metropolitan Police said 55 people were arrested in Parliament Square under Section 13 of the Terrorism Act 2000 for displaying placards in support of Palestine Action.
Greater Manchester Police said it had arrested 16 people on Saturday on suspicion of support of a proscribed organisation, adding that they remained in custody for questioning.
Eight people were arrested near Truro Cathedral in Cornwall after protesters gathered to show support for Palestine Action.
Avon and Somerset Police said 17 people were arrested during a protest in Bristol.
Palestine Action was banned after two Voyager aircraft were damaged at RAF Brize Norton in Oxfordshire on 20 June, an incident claimed by the direct action group, which police said caused about £7 million worth of damage.
Home Secretary Yvette Cooper announced plans to proscribe Palestine Action three days later, saying that the vandalism of the planes was “disgraceful” and that the group had a “long history of unacceptable criminal damage”.
The ban means that membership of, or support for, Palestine Action is now a criminal offence punishable by up to 14 years in prison, under the Terrorism Act 2000.
