London’s first-ever Muslim mayor, Sadiq Khan, attended a Holocaust remembrance event in one of his first acts as the city’s leader but his tweet about the visit sparked an anti-Semitic wave of comments on social media.

A day after his landmark win on Saturday, opposition Labour party politician Khan attended a Holocaust commemoration with more than 150 survivors and tweeted in a post shared more than 1,000 times: “At Yom HaShoah commemorations today. So important to reflect, remember and educate about the 6 million Jewish lives lost in the Holocaust.”

As the Labour Party defends itself from accusations of anti-Semitism among its ranks after former London Mayor Ken Livingstone said that Hitler was a supporter of Zionism, Khan faced a barrage of anti-Semitism from the Twittersphere after his visit of solidarity with London’s Jewish community.

Several posts alluded to the anti-Semitic trope that Khan is beholden to a Zionist lobby in the U.K.

At Yom HaShoah commemorations today. So important to reflect, remember and educate about the 6 million Jewish lives lost in the Holocaust.

@SadiqKhan How much did you get paid by the zionists?

Others focused on the figure of six million Jews who were killed in the Holocaust, denying the accuracy of this figure or going further and suggesting that the Holocaust itself was a fabrication.

“Have you plucked that figure of 6m out of thin air? What was the total population of Jews in 1940? Don’t distort history. Max 1m,” said one Twitter user.

At Yom HaShoah commemorations today. So important to reflect, remember and educate about the 6 million Jewish lives lost in the Holocaust.

@SadiqKhan How much did you get paid by the zionists?

Source: Newsweek