WASHINGTON (AFP) - A website that hosted anti-Semitic posts apparently authored by the man who allegedly killed 11 people at a Pittsburgh synagogue said on Saturday (Oct 27) it is being forced offline following the attack.

Gab.com, which is popular with white nationalists and members of the so-called alt-right, said its hosting provider Joyent would be suspending its services as of Monday morning, while PayPal has also reportedly banned the site.

"Gab will likely be down for weeks because of this," the site said on its Twitter account.

"We will continue to fight for free expression and individual liberty online for all people. Big tech can not stop us. The mainstream media can not stop us. The People will defend freedom against tyranny as they always have and always will," it tweeted.

Gab had earlier released a statement saying it had "zero tolerance" for violence or terrorism and was "saddened and disgusted by the news" from Pittsburgh, where six people were also injured in the Saturday morning shooting.

Gab said in a post that after learning of the attack, it had matched the name of the alleged shooter - Robert Bowers - to one of its account holders.

It then took down the Bowers account and immediately contacted the FBI, adding: "We will do everything in our power to work with law enforcement to see that justice is served."