Plastic bullets and tear gas were used to try and disperse large crowds in major cities and towns, with 30,000 riot police taking to the streets in Algiers alone.
There were also reports of journalists being targeted by state-sponsored thugs to stop reports of the disturbances being broadcast to the outside world.
But it was the government attack on the internet which was of particular significance to those calling for an end to President Abdelaziz Boutifleka's repressive regime.
Protesters mobilising through the internet were largely credited with bringing about revolutions in Egypt and Tunisia.
"The government doesn't want us forming crowds through the internet," said Rachid Salem, of Co-ordination for Democratic Change in Algeria.
Algeria shuts down internet and Facebook as protest mounts | Can we go for a third?