Authorities foiled an attempt by suicide bombers to blow up two oil installations with explosives-laden cars in near-simultaneous attacks Friday just days after al-Qaida threatened to strike facilities in the Persian Gulf. The four attackers and a guard were killed. The violence coincided with a feverish presidential election campaign in which President Ali Abdullah Saleh, facing his first real challenge since he became head of state in 1978, has reached out to the country's most strident Islamist movement, an alliance some believe will only embolden extremists. No group has claimed responsibility for the back-to-back bombings. But Prime Minister Abdul-Kader Bajammal said "investigators have uncovered all the details related to the two operations and the identity of the perpetrators," according to the official SABA news agency. He did not elaborate.