Supporters of Just Stop Oil began the action in the early hours of Friday morning at refineries near London, Birmingham and Southampton by climbing on to tankers and gluing themselves to roads.
Despite at least 34 arrests, the activists continued to disrupt oil terminals on Saturday morning and said they had gained access to further sites.
The group announced on social media that they had blocked Navigator terminals in Essex, posting photos of protesters in hi-vis jackets on top of a tanker and others blocking a road with a banner reading “Just Stop Oil”.
They said protesters had blocked access to the Titan Truck Park and revealed a secret underground network of tunnels leading to the site. The development means the main and emergency access roads to the critical oil terminals are closed.
“We need the government to stop funding new oil projects and we need it now! Our only means of highlighting this issue is mass civil resistance,” they said in a post on Instagram.