Rabbi Yosef Elitzur, from the West Bank settlement of Yitzhar, was detained by police on Thursday and questioned by investigators from the international crimes unit on suspicions of incitement to racism.

Elitzur and Rabbi Yitzhak Shapira wrote a book "The King's Torah" which condones the murder of non-Jews if they threaten the welfare of Jews, citing Jewish law to support the argument.

On Wednesday, Rabbi Dov Lior, who supported the book and has refused to appear for questioning by police on the matter, had his lawyer send a letter to the deputy state prosecutor explaining his position.

"The rabbi [Lior] asked me to tell you that he does not intend to answer to anybody on his opinion on Jewish law," Lior's lawyer wrote. "Your harassment of rabbis for their opinions on Jewish law contradicts the state's principles of religious freedom and freedom of expression."

"The King's Torah" was published in November. The preface of the book states that it is forbidden to kill non-Jews but the book then describes the context in which it is permitted to do so.

According to the book, it is permissible to kill a non-Jew who threatens Israel even if the person is classified as a Righteous Gentile. The book says that any gentile who supports war against Israel can also be killed.