JERUSALEM, July 3 (Dan Williams/Reuters) - Israeli police briefly detained a leading rabbi on Sunday as part of a widening probe into a treatise suspected of inciting the murder of Arabs.

The investigation has pitted authorities in the Jewish state against far-right West Bank settlers and has led to scuffles outside government institutions in Jerusalem and a sit-down protest that choked off the main highway to Tel Aviv.

Rabbi Yaacov Yosef was seized by detectives on his way back from morning prayers, witnesses said, in a tactic similar to the arrest last week of a senior West Bank rabbi whose followers responded with street protests.

They commandeered the car and took it away, together with my dad, to an undisclosed destination, Yosef's son Yonatan told Israel Radio. The rabbi was freed after an hour, police said.

The clerics had ignored a police summons to be questioned over endorsements for The King's Doctrine, a book written by a more obscure settler rabbi offering justifications from scripture for killing innocent gentiles during religious war.

Revenge, including strikes on the blameless and on babies, is necessary and important in fighting and defeating evil, read a passage excerpted on Israel's top-rated television news.

Israeli security officials fear such edicts could fuel Jewish attacks designed to scupper the eviction of settlers from occupied land they regard as theirs by biblical birthright but where Palestinians, with international support, seek statehood.

A police spokesman said Yosef had been interrogated in connection with incitement to racism and violence before being let go. Dov Lior, chief rabbi for the hardcore settlement of Kiryat Arba, was similarly questioned and released last week.

OUTRAGE

It must be made unequivocally clear that we are a state of law and that no one is above the law, Deputy Prime Minister Dan Meridor told Israel's Army Radio.

The King's Doctrine, he said, is a book that in an ugly, racist manner appears to permit, in certain ways and under certain circumstances, the killing of a person because he is not Jewish ... This is outrageous and demands a response.

In statements carried by Israeli media, the rabbis and their representatives have not openly called for sectarian bloodshed.

But they have been dismissive of Israel's authority to rein them in -- which, coupled with the pace of police actions, has prompted some political commentators to warn of a dangerous drift between state and synagogue.

Yosef's father, Rabbi Ovadia Yosef, is mentor to Shas, the powerful religious party that is junior partner in Prime Minister Benjamin Netanyahu's conservative coalition government.

Amram Yosef, another son of the detained rabbi, said his father had refused to undergo police questioning voluntarily because he will not permit the Bible to be investigated.

He wanted it to be forced on him. He was calm. He expected it, Amram Yosef said, adding: I believe we will be seeing demonstrations over the course of the day.

The other son, Yonatan, said police should focus instead on all of those professors and doctors -- a reference to critics of the religious right from among Israel's secular majority.

(Editing by Michael Roddy)