"The Shin Bet, with the assistance of the army and the police, have arrested a number of those involved in the murder of Sarya Ofer," the agency said in a statement.
It was not yet known if Friday's murder was politically-motivated.
The Shin Bet said Odeh Farid Harub, 18, and Bashir Ahmed Harub, 21, had confessed to the killing of the retired army colonel at his isolated Jordan Valley home.
They were among three men from the southern West Bank village of Dir Samat, near Hebron, arrested yesterday "following intelligence information."
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The Shin Bet said their account matched a statement by Monique, who escaped with injuries after her husband was bludgeoned to death, saying youths from the Hebron area had came to the house "under suspicious circumstances."
The police said after the killing that it was most likely the work of Palestinian militants, while right-wing politicians said peace talks with the Palestinians should be suspended as a result.
But media have speculated it could have been the result of a bungled burglary attempt or the settling of a personal dispute.