German authorities have banned the most influential internet website of Antifa – the country's militant left -- in the wake of violence that occured last month outside the G20 summit in Hamburg.

In an unprecedented move against violent left-wing extremism, Germany’s Interior Ministry informed the owners of the left-wing site about the crackdown Friday, the Local reported.

Interior Minister Thomas de Maizière claimed the website helped incite the violence in Hamburg and warned of “serious consequences” of left-wing radicalism, the New York Times reported.

“The prelude to the G-20 summit in Hamburg was not the only time that violent actions and attacks on infrastructural facilities were mobilized on linksunten.indymedia,” the minister said, identifying the website.

He also said the site tried to “legitimize violence against police officers,” which he described as an “expression of an attitude that tramples human dignity.”

“This is absolutely unacceptable and incompatible with our liberal democratic order,” he added.

According to the Local, Germany’s internal spy agency once described the website, which has operated since 2008, as “the most important platform for violent left-wing extremism in Germany. For years it has been providing a forum for people to publish first-hand reports on left-wing crimes.”

The platform has been used to coordinate actions against various causes – as the site’s forum allowed people to post anonymously – and played a key role in organizing the riots in Hamburg, the report said.

Local police said at the time that the militants set up street barricades, looted supermarkets, torched cars and attacked police officers with Molotov cocktails, iron rods, and slingshots.

The violent clashes between the Antifa and police led to around 476 police officers being injured, while around 186 demonstrators were arrested and 225 were temporarily detained.

The Interior Ministry said the website was shut down because it “goes directly against the law in both its aims and actions,” Spiegel reported.

The police, meanwhile, searched the properties connected to the owners of the radical website in the German state of Baden-Württemberg. “At the moment several premises are being searched,” said Thomas Strobl, the state’s interior minister.

“This step marks a major blow against the extreme left in Germany,” he added.

The computers and other evidence have reportedly been seized, although no arrests in connection to the investigation have been made.

Following the announced closure, the extremist website now directs visitors to a “what to do” article calling the government’s move an “authoritarian crackdown.”

It also urges people to spread “revolutionary material and ideas everywhere” and come up with “alternative ways to communicate with each other and the general public in times of intensifying state censorship and control.”

The Associated Press contributed to this report.