The attacks, in which 49 worshipers were murdered, were committed by a white supremacist who live-streamed his actions to Facebook.
Speaking at the funeral of a former Turkish minister, Erdogan said that "with this attack, hostility towards Islam, that the world has been idly watching and even encouraging for some time, has gone beyond individual harassment to reach the level of mass killing."
"It is clear that the understanding represented by the killer that also targets our country, our people and myself, has started to take over Western societies like a cancer," he went on.
"If measures are not taken right away, news of other disasters will follow this one... I am calling on the world, in particular the West, to take quick measures."
Erdogan wrote on Twitter earlier on Friday, "May Allah have mercy on the victims and grant a speedy recovery to the wounded."