Activists from Greenpeace have blockaded all entrances to the BP headquarters in London with demands to make an end to all new oil and gas exploration.

The campaigners arrived at 3am on Monday and encased themselves in heavy containers before the oil company’s annual general meeting on Tuesday.

The containers, each weighing several tonnes, are being used to blockade all five entrances to prevent staff from entering BP’s offices in St James’s Square.

Two activists are encased in each of the five containers with enough provisions to last at least a week. Another 15 activists are occupying the top of the boxes after abseiling down the side of the building.

Greenpeace said it was carrying out the action because BP was behaving as if the climate emergency was not happening.

The group accused BP of “fuelling” the emergency and called on the company to “end the search for new oil and gas and start a rapid switch to 100% renewables”.

The activist Paul Morozzo, who spoke to the Guardian by phone from inside one of the boxes, said that the climate situation was so serious so it needed action. Activists are ready to stay for as long as they can.