The mass shooting at a Pittsburgh synagogue has drawn scrutiny on the Gab social media site after the suspect was found to have used it to express anti-Semitic views.

The website, Gab.com, said it suspended his account and contacted the authorities after the arrest but it was not enough to stop internet services from cutting ties with it.

The website, which is popular with white nationalists and members of the so-called alt-right, said on Saturday night it was being forced offline following the attack that left 11 people dead.

It 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.