Extinction Rebellion protesters have blocked roads outside printing presses owned by media mogul Rupert Murdoch.
The News Corp sites, in Broxbourne, Hertfordshire, and Knowsley, Merseyside, produce copies of several national papers.
Campaigners said they wanted to prevent titles including The Sun, The Times and the Daily Mail from reaching shops on Saturday.
Hertfordshire Police said there were about 100 protesters at Broxbourne.
Extinction Rebellion said it was also holding a protest in Holytown, near Motherwell, to disrupt distribution of The Scottish Sun.
It has accused the newspapers and their owners of "failure to report on the climate and ecological emergency" and "polluting national debate" on dozens of social issues.
Hertfordshire Police said its officers were engaging with the group and "working to facilitate the rights of both the protestors and those affected by their presence".
Extinction Rebellion has planned 10 days of action and demanded the government declare a climate and ecological emergency.
On Thursday, more than 300 people were arrested during protests in central London.
Campaigners said they wanted to prevent titles including The Sun, The Times and the Daily Mail from reaching shops on Saturday.
Hertfordshire Police said there were about 100 protesters at Broxbourne.
Extinction Rebellion said it was also holding a protest in Holytown, near Motherwell, to disrupt distribution of The Scottish Sun.
It has accused the newspapers and their owners of "failure to report on the climate and ecological emergency" and "polluting national debate" on dozens of social issues.
Hertfordshire Police said its officers were engaging with the group and "working to facilitate the rights of both the protestors and those affected by their presence".
Extinction Rebellion has planned 10 days of action and demanded the government declare a climate and ecological emergency.
On Thursday, more than 300 people were arrested during protests in central London.