The PSNI said the women had been held on suspicion of criminal damage.
Videos circulating online show one woman being spoken to at length by PSNI officers close to a cash machine.
An MLA said she had been arrested for protesting outside Barclays Bank.
There has been criticism of the bank’s financial ties with arms companies that sell weapons to Israel. Several other branches of Barclays across the UK have previously been targeted.
The woman tells officers: “Children are dying in Gaza”.
The woman – understood to be a prominent Palestinian activist – is then led away to the back of a PSNI vehicle.
A second woman was also arrested at the protest.
The PSNI said: “Police received a report relating to a protest in the Castle Place area of Belfast city centre on Saturday morning, May 24.
“Officers attended and two people have been arrested on suspicion of criminal damage.
“The women – one aged in her 70s and the other in her 50s – are in custody, assisting with police enquiries at this time.”
The pair were taken to Musgrave PSNI station, where campaigners gathered to show their support.
Sinn Fein MLA Pat Sheehan criticised the arrests.
He said it was “disgraceful” that one is an “elderly Jewish woman who has consistently and bravely campaigned for an end to Israel’s genocide in Gaza”.
“Highlighting the genocidal, inhumane slaughter of defenceless civilians — and those who enable it — is not a crime,” he said.
The PSNI arrested two campaigners.
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Mr Sheehan added: “We will be raising our concerns directly with the PSNI.”
People Before Profit MLA Gerry Carroll said: “All over the world Israel’s legitimacy has utterly crumbled. And so the establishment is ramping up its repression to try and silence protestors.”
SDLP councillor Paul Doherty said he was “deeply concerned” by the arrests.
He said they happened during a peaceful protest.
“Barclays should rightfully be boycotted due to their financial ties with companies that supply weapons and military technology to Israel,” he added.
“I stand in full solidarity with these activists and call for them to be released without charge.”
Barclays Bank has been contacted for comment.