Corbyn apparently gave a speech at a 2011 conference in Geneva organized by the European Network to Support the Rights of Palestinian Prisoners (UFree).
The conference was uncovered on the Twitter account "The Golem," who also posted a link to the conference's report.
The conference was attended by Raed Salah, leader of the northern branch of the Islamic Movement in Israel. In a 2007 speech, Salah accused Jews of using children's blood to bake bread, according to Israeli newspapers. After a series of court battles, he was convicted of incitement to racism by the Jerusalem District Court in November 2014.
Salah has also served time in Israeli prison for funding Hamas, and sailed on the Mavi Marmara in the 2010 Gaza protest flotilla. He was present during the subsequent raid on the ship by IDF commandos, which left nine Turkish citizens dead.
Also in attendance at the event was a former IRA volunteer, Gerry MacLochlainn, and former Labour Party MP Martin Linton, who apologized after warning voters of the "long tentacles of Israel in [England] who are funding election campaigns and putting money into the British political system for their own ends," according to a report from the Jewish Chronicle.
Yonah Jeremy Bob contributed to this report.