Massive anti-war protests have erupted across Russia for the fourth day in a row, as Vladimir Putin's war on dissent took an ominous turn on Sunday after the state threatened to jail 'traitors' who provide any form of help to embattled Ukraine for 20 years.

Russians in cities spanning from Moscow to Siberia have taken to the streets again on Sunday to protest the Kremlin's invasion of Ukraine on Thursday.

Peaceful demonstrators in the Russian capital Moscow and St Petersburg chanted 'No to war' before police in riot gear grabbed them and dragged them into police vans.

According to the OVD-Info rights group that tracks political arrests, by Sunday afternoon Russian police had detained at least 356 Russians in 32 cities.

Protests against Putin's unpopular war started on Thursday and have continued for four days in a row, despite police swiftly moving to detain hundreds of people each day.  

The Russian state has launched a sweeping crackdown on internal criticism of the Ukraine war, and today dramatically accused anyone who provides help to the country of 'treason to the Motherland'.