The protesters are supporting Julian Assange, the Wikileaks founder who has been living in the embassy since June 19.
Assange is avoiding extradition to Sweden, where officials want to question him about alleged sexual misconduct.
Assange's supporters fear that handing him over to Sweden will open the door to a trial in the United States, where some politicians have labeled him a terrorist.
Ecuadorian officials won't back down from their promise of asylum to Assange, despite pressure from U.S., U.K. and Swedish officials. They think he faces a serious threat of political persecution.
Meanwhile, in Ecuador, many support their country's decision, and are angered by the U.K.'s efforts to undermine it.