Yemeni authorities say security forces have foiled two separate suicide attacks on oil installations, killing all four attackers.
Officials say one security guard was also killed in the exchange of gunfire at one of the installations.
They say the attackers using booby-trapped vehicles and dressed as oil workers tried to hit the facilities during the change of shifts early Friday morning.
They say the targets were the refinery in Mareb province and the storage deport at the Al-Dubba port in the province of Haramut.
The attacks took place just days before Yemen is to hold presidential and local council elections.
President Ali Abdullah Saleh, who has ruled the Arab country since 1978, is seeking another seven-year term in next week's ballot.
Yemen is the ancestral homeland of al-Qaida chief Osama bin Laden.
In 2000, al-Qaida-linked terrorists carried out a suicide attack on a U.S. navy ship anchored at the port of Aden. Seventeen American sailors were killed in that attack.
Two years later, militants attacked the French supertanker Limburg.
Some information for this report was provided by AP, AFP and Reuters