Italian police warned on Thursday that anti-vaccine campaigners had called for armed attacks during planned anti-government protests this weekend, and that eight people were being investigated for incitement to crime.
A police statement said searches had been conducted in six Italian provinces, including Milan, Rome and Venice, and that the eight placed under investigation were part of a group calling itself "the warriors" on the Telegram messaging app.
Investigators suspect they were preparing to carry out attacks during demonstrations scheduled in Rome on Saturday and Sunday against the government's Green Pass health documents allowing entry to many venues during the COVID-19 pandemic.
The investigators suspect the group was using Telegram to organise its activities and to encourage others to carry out attacks in other cities, the statement said.
It did not say what the targets of any attacks might be.
There was no immediate comment from anti-vaccine campaigners.
The Green Pass is a digital or paper certificate that shows whether someone has received at least one COVID-19 vaccine dose, has tested negative or has recently recovered from the virus.
It was introduced this summer to try to prevent infections and encourage people to get vaccinated. It was initially needed to enter many cultural and leisure venues, but its scope has gradually been widened.
The scheme has caused protests by some Italians who say it tramples on freedoms, but only a handful of people showed up at a mass demonstration organised last week to block railway traffic across the country.