Climate group Just Stop Oil said 51 of its supporters are disrupting seven petrol stations across London.
In some locations, activists rendered fuel pumps unusable by breaking their display glass or covering them with spray paint.
At others they blocked access by sitting on the road with banners.
The action started at around 6am.
The Metropolitan Police said it made five arrests after an incident at a petrol station in west London.
A spokesman said: “Police were called at 6.29am on Friday to reports of protesters damaging pumps at a petrol station in Talgarth Road, Hammersmith.
“Officered attended and within approximately 10 minutes had arrested four men and one woman on suspicion of criminal damage.
