A married Christian couple have been arrested on suspicion of criminal damage after paint was daubed on the gates outside Downing Street.
Scotland Yard said it was called to the incident around 11.45am on Friday.
Photos from the scene showed paint resembling 'bloody' handprint on the black gates that fence off the famous street.
The arrest followed a protest calling for a ceasefire in the conflict between Israel and Hamas.
Virginia Moffat, 58, and Chris Cole, 60, were named by campaign group FigTree as the arrested pair.
The couple, from Dorset, said the Government had “blood on its hands” after refusing to demand Israel end its bombing of Gaza, according to a statement by FigTree.
The Christian protesters called it “a massacre of biblical proportions”.
In a statement, Ms Moffat and Mr Cole said: “Britain’s and Israel’s justification for this slaughter is that Israel is acting in ‘self-defence’; that the deaths of innocents are to be regretted, but Israel must be allowed to act in its own defence.
“This is nonsense. Again and again, leading international lawyers have clearly stated that ‘self-defence’ cannot justify the slaughter of so many innocent Palestinians.”
They added: “As bombs rain down on Gaza, destroying homes, hospitals, families, schools, cultural centres, mosques, churches and civic buildings, we cannot help but act.
“By refusing to back a ceasefire, and continuing to supply arms to Israel, our government is complicit with this slaughter.”
Met Police Chief Superintendent Joseph Mcdonald said: “We have been clear that we will facilitate lawful protest but where this strays into criminality we will take swift action.
"Arrests were made within minutes of this incident taking place and both people are now in custody."Anyone with information that could assist police is asked to call 101 or ‘X’ @MetCC and quote CAD2366/29Dec.
