The arrests have been made across the capital as environmentalists stage two weeks of action aimed at forcing governments to do more to tackle climate change.
The embassy protest near Trafalgar Square is against what activists claim is “the genocidal attacks being waged against Brazil’s indigenous peoples”.
They on Tuesday blocked the entrance to Selfridges in Oxford Street in a protest against clothes production which they claim is damaging the environment.
They daubed the pavement outside with a black substance representing an oil spill and smeared the black liquid over themselves as they stood with their banners covering the entrance.
Business groups have accused the protesters of severely damaging the London economy and jeopardising its recovery after the pandemic lockdowns.
The two weeks of action has already targeted Trafalgar Square and Covent Garden where a giant table was set up to blockade shopping streets.
That was dismantled on Tuesday by specialist officers while demonstrators who had glued themselves to the structure were removed.
On Sunday officers arrested ten people after protesters scaled the Guildhall in the Square Mile.