JERUSALEM — The complex, multistage attack that caused thousands of Hezbollah pagers and handheld radios to explode across Lebanon over the last two days appears to have been meticulously mapped out.

       Israel, which rarely comments on its intelligence operations abroad, has neither claimed nor denied responsibility for the attack, which continued into a second day Wednesday as more devices exploded across Lebanon. The Israelis did not inform the United States about the specifics of the attack before it took place but told Washington afterward through intelligence channels, according to two U.S. officials. Like others in this story, they spoke on the condition of anonymity to discuss sensitive matters.