Yemen ? Authorities foiled an attempt by suicide bombers to blow up two oil installations with explosives-laden cars Friday, days after al-Qaida threatened to strike facilities in the Persian Gulf. The four attackers and a guard were killed.

The violence coincided with an election campaign in which President Ali Abdullah Saleh, facing his first real challenge since he became head of state in 1978, has been reaching out to the country’s most strident Islamic movement.

No group claimed responsibility for Friday’s attacks. 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 news agency.