Twenty climate activists have been arrested during protests targeting two oil sites.

Police Scotland said arrests at Grangemouth oil refinery were over alleged public order offences and a breach of the peace.

Climate campaign group This Is Rigged blockaded the Ineos site at Grangemouth and the Nustar Clydebank oil terminal early on Wednesday.

Activists blocked gates, climbed on pipes and sat on top of tankers, vowing to “shut down the Scottish oil industry”, with the disruption forcing the closure of a tanker terminal at the Ineos refinery for several hours.

An Ineos spokesman previously confirmed that manufacturing at the site was not affected.

Police Scotland said on Thursday afternoon that a “small group” of protesters remain at the Clydebank site, along with police officers.

The campaign group said three activists are on top of the silo at the Clydebank terminal and claimed there has been “no oil tanker activity since they arrived at around 4am yesterday morning”.

On Wednesday, officers used specialist equipment including ropes and cranes to remove activists sitting on top of an oil tanker at Grangemouth.

Fuel tankers were spray painted with “This is Rigged” and “stop oil”.

Assistant Chief Constable Emma Bond said: “Twenty people have been arrested and charged for offences under section 68 of the Public Order Act and breach of the peace at the Ineos site in Grangemouth on Wednesday, 19 July.

“Decisions about how to police protests require us to balance complex and often competing rights and issues. We have a legal duty to protect the rights of people who wish to peacefully protest or counter-protest.

“The guiding principles of policing protests are the safety of protesters, the public and police officers involved, preventing criminal behaviour or disorder and deescalating tensions.

“A small group remains gathered at the oil terminal at Rothesay Dock in Clydebank and officers are currently in attendance.”

Those arrested at the Ineos site were 11 women, aged 72, 69, 61, 60 35, 32, 24, 23, 22, 22 and 21, and nine men, aged 56, 36, 32, 29, 28, 27, 25, 22 and 21.

All are due to appear on undertakings at Falkirk Sheriff Court at a later date.

This Is Rigged posted on Twitter: “Grangemouth supplies 90% of Scotland’s oil. We have stopped oil leaving this site, as well as Nustar Terminal in Clydebank. We have no plans to stop.”

They added: “The action is the first in a sustained series of actions, in which the group has vowed to shut down the Scottish oil industry.”

The group called on the Scottish Government to implement a just transition for oil and gas workers “instead of assisting billionaires like (Ineos owner) Jim Ratcliffe”.

Nustar has been contacted for comment.