SANAA, Yemen — Yemen has foiled a plot by al-Qaida to seize two major oil and gas export terminals and a provincial capital in the east of the country, the government said on Wednesday, as Western embassies remained in lock-down in Sanaa and a spy plane circled above.

The announcement of the thwarted plot comes after warnings of potential attacks by militants prompted Washington to shut diplomatic missions across the Middle East and Africa last week and to issue a global travel warning.

Attention shifted to Yemen when U.S. sources said intercepted communication between al-Qaida leader Ayman al-Zawahiri and the Yemen-based wing of the militant group was partly what provoked the measures.

Both the United States and Britain withdrew some of their diplomatic personnel from Yemen on Tuesday and reiterated calls to their nationals to leave the country. Other European countries, such as France and Norway, also shut their embassies.

U.S. ally Yemen, one of the poorest Arab countries, is the base for Al-Qaida in the Arabian Peninsula (AQAP), one of the most active branches of the network founded by Osama bin Laden, and militants have launched attacks from there against the West.

Rajeh Badi, press adviser to Yemeni Prime Minister Mohammed Salem Basindwa, said it was the discovery of this al-Qaida plot which prompted the U.S. security measures.

The plan was uncovered with Western and Arab help and also involved smuggling explosives into Sanaa on Sunday to carry out attacks there, Badi said.

"The plot involved using dozens of al-Qaida militants dressed in Yemeni army uniforms to storm the facilities on the night of the 27th of Ramadan," he told Reuters.

HIGH ALERT, ROCKY TRANSITION

Muslims celebrate the 27th of the holy Muslim month of Ramadan as they believe it is the night on which the Koran was revealed to the Prophet Mohammed.

"The plot aimed to seize the al-Dabbah oil export terminal in Hadramout and the Balhaf gas export facility, as well as the city of Mukalla," Badi told Reuters, referring to the capital of the eastern province of Hadramout.

He said the plan was foiled by putting security forces on high alert and by tightening entry procedures to these facilities.

An official who oversees security for oil companies operating in Yemen said the al-Qaida plot had apparently intended to kill foreign experts working at the facilities or take them hostage.

Plans for such an attack on the Balhaf and Al-Dabbah plant will have raised alarm bells in Washington.

In January, Islamist gunmen attacked an Algerian gas plant, seizing hundreds of hostages before the army stormed it four days later. Dozens of foreign workers were killed.

Yemen is going through a rocky political transition after the ouster of long-serving President Ali Abdullah Saleh in 2012, while battling a dogged al-Qaida insurgency, grinding poverty and a simmering secessionist movement in the south.

In 2011, Islamist militants exploited the power vacuum and chaos caused with Arab Spring protests against Saleh and captured several southern towns. It took a U.S.-backed military offensive launched last year to drive them out in which hundreds died.

In its bid to eradicate AQAP, the United States is waging a campaign of drone strikes to hunt the militants, scattered across Yemen and its impassable desert or mountain terrain.

Washington's fears over al-Qaida in Yemen re-emerged after Nigerian Umar Farouk Abdulmutallab, who had been trained by AQAP in Yemen, tried to blow up a Detroit-bound plane with a bomb in his underpants on Christmas Day 2009.

The United States had already suffered a serious attack by al-Qaida militants in Yemen in 2000, when suicide bombers rammed a boat full of explosives into the side of the USS Cole while the warship was fueling in the port of Aden. Seventeen U.S. sailors were killed in the explosion.

In the latest strike on Wednesday, the fifth in two weeks, six suspected militants were burned to death when a drone fired at two vehicles in the southern Shabwa province, witnesses and local officials said.

The $4.5 billion Balhaf gas plant, which opened in 2009, is one of the most strategic projects in Yemen. It is run jointly by Yemen LNG and France's Total.

Al-Dabbah is the main oil export facility in eastern Yemen. Some 90 percent of Yemen's foreign currency revenues come from oil and gas and represent about 70 percent of its exports.

CLOSE BUT COMPLEX

Stability to Yemen — a country which is close to major shipping lanes and torn by regional and sectarian separatism and tribal violence as well as the al-Qaida insurgency — has been a priority for the United States, and the two countries have a close but complex relationship.

Tuesday's evacuation of some diplomats angered Yemeni officials.

Yemeni Foreign Minister Abu-Bakr al-Qirbi said the Western measures effectively serve the goals that the "terrorist elements are seeking to achieve."

Badi said Western countries have assured Yemen that the embassies will reopen after the Eid al-Fitr holiday, due to start this week.

The official said the information over an al-Qaida plot began reaching Yemeni security authorities in early July, with the start of the fasting month of Ramadan, with chatter intensifying two weeks ago.

He said Yemen responded by tightening security around Western missions and beefing up the military around oil and gas facilities around the country.

Yemen also tightened security measures around the capital.

Witnesses said a reconnaissance aircraft hovered in the sky above the capital for hours on Tuesday and had returned again on Wednesday.

Yemen's Supreme Security Committee issued a statement earlier this week saying it had information al-Qaida was plotting attacks during Eid al-Fitr, this week's Muslim holiday that marks the end of the Ramadan fasting month.

The committee also published a list of 25 senior al-Qaida militants it said were being sought by security forces and offered a bounty of 5 million Yemeni riyals ($23,000) for information leading to their capture.