ADEN: Yemen said Wednesday it had foiled an al Qaeda plot to storm a Western-run oil terminal and seize a provincial capital, as a terror alert kept US Middle East missions closed.

The jihadist network's feared Yemeni affiliate planned to assault the Canadian-run Mina al-Dhaba oil terminal on the Arabian Sea coast and take staff hostage, including Western expatriates, government spokesman Rajeh Badi told AFP.

A nearby export facility for oil derivatives was targeted too, Badi said.

The terrorist organisation also plotted to seize the nearby Hadramawt provincial capital Al-Mukalla, a port city of some 100,000 people, and the Ghayl Bawazeer area to its north, where they briefly declared an Islamic emirate earlier this year, Badi said.

“If they were to fail in seizing control of the facilities, the plan was to take foreign experts away as hostages,” he said.

The attack was planned for Monday, which coincided with the 27th day of the Muslim fasting month of Ramadan and was the second day of a mass closure of US missions across the Middle East and North Africa.

The plot was foiled around two days before it was due to be launched, Badi said.

Both Washington and London pulled diplomatic personnel out of Sanaa on Tuesday citing intelligence reports of an imminent attack by the Yemen-based al Qaeda in the Arabian Peninsula (AQAP).

The United States took the unusual step of closing some 25 diplomatic missions in the Muslim world on Sunday, and then extending the closure for a week at 19 of them, in response to what it said was a credible and imminent threat of a major al Qaeda attack.

An intercepted conference call between al Qaeda leader Ayman al-Zawahiri and top operatives was the trigger for the closures, online journal The Daily Beast reported on Wednesday, citing US intelligence sources.

It said more than 20 al Qaeda operatives from across the globe were on the call, including representatives of Nigeria's Boko Haram, the Pakistani Taliban and al Qaeda in Iraq as well as AQAP.

In the call, Zawahiri reportedly named AQAP chief Nasser al-Wuhayshi, as the operational controller of the group's affiliates throughout the Muslim world.

“This was like a meeting of the Legion of Doom,” the Daily Beast quoted a US intelligence officer as saying.

While the closures span cities across the Arab world, the focus of concern has been Yemen, where Washington has been fighting a drone war against AQAP militants for several years.

US State Department spokeswoman Jen Psaki said on Wednesday Washington's embassy in Sanaa remains closed, “and we continue to evaluate the threats on a daily basis”.

Tribal sources said a US drone killed seven suspected jihadists in Shabwa province, to the west of Hadramawt, on Wednesday, the second such strike in as many days.

The early-morning attack in the town of Nasab destroyed two vehicles, the sources said. It was the fifth US drone strike in Yemen since July 28. At least 24 suspected Al-Qaeda militants have been killed.

On August 1, President Barack Obama hosted his Yemeni counterpart Abdrabuh Mansur Hadi for White House talks on their joint struggle against the jihadists.

AQAP is seen as the global Islamist militant network's most capable franchise following the decimation of al Qaeda's core leadership in Afghanistan and Pakistan in recent years.

Washington has launched scores of drone strikes in Yemen, where AQAP thrives in vast, lawless areas largely outside the government's control.

In recent days, Yemeni authorities beefed up security in Sanaa, where they feared the attack would be launched.

But they responded angrily to the withdrawal of Western diplomats. They said they recognised the safety fears but that the pullout “serves the interests of the extremists.” “It undermines the exceptional cooperation between Yemen and the international alliance against terrorism,” the foreign ministry said.

The Yemen-based AQAP has attempted several attacks on the United States, including a failed bid to bring down a passenger plane by a man wearing explosives in his underwear and another to send bombs concealed in printer cartridges.

The intent of the foiled plot on oil facilities appears to have been similar to a spectacular January attack by Islamist militants on a gas plant deep in the Algerian desert.

Thirty-eight hostages, all but one of them foreigners, lost their lives, along with 29 militants, in the four-day siege at the In Amenas plant, which was ended by the Algerian army.