Extinction Rebellion protesters are trying to shut down the BBC by blockading the entrances and climbing onto the canopy of Broadcast House.
The move follows the group abandoning efforts to close City Airport for three days after only one day.
Over 1000 climate change activists have been arrested since two weeks of planned protests began on Monday.
Earlier today protesters began blocking workers from entering or leaving the main entrance of Broadcasting House, the headquarters of the BBC.
The group have not said how long they plan to blockade the BBC.
A spokesperson for Extinction Rebellion said: "Six people have been arrested after glueing their hands to the main doors.
"Hundreds of people are now in the forecourt listening to talks on the climate and ecological emergency from doctors, farmers, scientists and more."
BBC News podcast producer Georgia Coan posted footage to Twitter of two Extinction Rebellion protesters who climbed onto the BBC building.
Earlier, Financial journalist Paul Lewis tweeted that staff had been locked out of the building by the protesters.
He wrote: “Locked out of BBC by extinction rebellion.”
However, BBC Radio 5 presenter Nihal Arthanayake claimed that it was still easy for staff to enter the building.
He tweeted: "As I walked into the BBC this morning every member of @ExtinctionR apologised for the disruption.
"I got into work very easily. BBC people complaining should get a grip."
Last night the group were mocked as a "quasi-religious death cult" by columnist Julia Hartley-Brewer on BBC's flagship current affairs programme, Question Time.
