THE US has sharply escalated its drone war in Yemen, with military officials in the Arab country reporting 34 suspected al Qaeda militants killed in less than two weeks.

That included three strikes on Thursday in which a dozen people died, as the action against al Qaeda in the Arabian Peninsula, as the Yemen branch is known, intensified. It comes amid a global terror alert issued by Washington.

One Middle East official says the upsurge is due to its leaders leaving themselves more vulnerable by moving from their normal hideouts toward areas where they could carry out attacks.

The recent drone strikes, which all targeted cars, have become a near-daily routine since they began on July 27. So far, they have been concentrated in remote, mountainous areas where al Qaeda's top five leaders are believed to have taken refuge.

But drones also have been seen and heard buzzing for hours over Sanaa, worrying residents who fear getting caught in the crossfire.

In the last fortnight, drone attacks have killed 34 suspected militants, according to information provided by Yemeni security officials.

Authorities in Yemen said they had discovered an al Qaeda plot to target foreign embassies in Sanaa and international shipping in the Red Sea.

And they said a group of al Qaeda militants have entered Sanaa and other cities to carry attacks. It issued a list of 25 al Qaeda wanted militants.