Sheikh Khaled Al-Mughrabi, a fiery preacher whose lessons at al-Aksa Mosque frequently include anti-Semitic motifs, was arrested by security forces Sunday, according to Wafa, the Palestinian Authority news agency.The arrest came after an extended investigation in which the Palestinian Media Watch NGO supplied police with multiple videos of his sermons, Itamar Marcus, the group’s founder, told The Jerusalem Post.In early June, the Simon Wiesenthal Center wrote to King Abdullah of Jordan and Palestinian Authority President Mahmoud Abbas, urging them to denounce the preacher after he publicly endorsed medieval blood libels during a sermon.During his homily, Mughrabi had asserted that “the Children of Israel... would look for a small child, kidnap and steal him, bring a barrel called the barrel of nails.... They would put the small child in the barrel and his body would be pierced by these nails. In the bottom of the barrel, they would put a faucet and pour the blood.”Such actions, he said, were directly responsible for the Holocaust, adding that Jews masterminded the September 11 attacks and control Hollywood.“It doesn’t matter what they said. What I said, it’s recorded. Everything that I said is recorded. What I said is that story happened in Europe and many countries in Europe and I still say that,” he told the Post when asked if he was an anti-Semite.During a sermon, Mughrabi said he had only been trying to save the Jews from the fires of hell.He did “not talk about the Children of Israel because we hate the Children of Israel, [but] rather the opposite. It is the Children of Israel who hate all the nations,” he claimed.Last week, Mughrabi was filmed promoting martyrdom to children in an alley near the Temple Mount.In a four-minute video – taken near the Temple Mount published online by the Middle East Media Research Institute – he told the group of boys and girls, that a “martyr is absolved with the first drop of his blood.”The sheikh went on to state that, after being killed, martyrs go on to marry “two virgins in paradise” and can “vouch for 70 family members on Judgment Day.”In his last video before his arrest, published by Palestinian Media Watch on Sunday, Mughrabi alleged that half of the world’s wealth is in the hands of the Rothschild family and that Jews controlling the pharmaceutical industry “create and spread disease so they can sell medicine for it.”Commenting on the arrest, Marcus said he had provided the police with material beginning several weeks ago.Because the crimes occurred at the Aksa mosque, he believed law enforcement “had to wait” until they received approval from the political echelon.During a 2012 speech in east Jerusalem, the PA’s Mufti of Jerusalem, quoted an Islamic legend that, at the end of days, Jews will hide behind trees that call out “Oh Muslim, servant of Allah, there is a Jew behind me, come and kill him.”Despite wall-to-wall condemnations, including from Prime Minister Benjamin Netanyahu, the Mufti was not prosecuted, Marcus said.“I think that it’s critical that incitement to hatred and incitement to violence and murder is prosecuted when it comes from the Palestinian side,” he said. “When their leadership presents the killing of Jews as a religious obligation, this is the worst kind of incitement to murder that can be. It must be prosecuted and it must be stopped.”Daniel K. Eisenbud contributed to this report.