Yemen's security forces on high alert on fears of al-Qaeda attack Security forces in Yemen have been placed on high alert amid fears of an al-Qaeda-linked attack. Foreign diplomatic missions and government offices are being protected by ground troops and tanks. The move comes as the Obama administration stepped up its drone campaign with a series of four strikes in quick succession, after intercepting messages between two prominent al-Qaeda leaders. U.S. officials say this intelligence indicated that al-Qaeda's leader had urged the group's Yemeni branch to attack Western targets. Ayman al-Zawahiri, the al-Qaeda leader that replaced Osama bin-Laden is said to have contacted Yemen-based Nasser al-Wuhayshi, head of al-Qaeda in the Arabian Peninsula. The drone strikes ended a seven-week spell with no U.S. activity in the region, killing four presumed al-Qaeda militants. As Washington and London evacuate their diplomats from the capital Sanaa in a climate of escalating tension, there are now mounting fears of al-Qaeda liquid bomb attacks. More about: Al-Qaeda, Terrorism, United Kingdom, USA, Yemen