DUBAI, United Arab Emirates (AP) — The assault on the beating heart of Saudi Arabia's vast oil empire follows a new and dangerous pattern that's emerged across the Persian Gulf this summer of precise attacks that leave few obvious clues as to who launched them.

Beginning in May with the still-unclaimed explosions that damaged oil tankers near the Strait of Hormuz, the region has seen its energy infrastructure repeatedly targeted. Those attacks culminated with Saturday's assault on the world's biggest oil processor in eastern Saudi Arabia, which halved the oil-rich kingdom's production and caus...