A senior member of al Qaeda's Yemen wing who the Yemeni government said it killed has emerged on an internet forum, threatening to carry out attacks in the United States.

Yemen declared an open war on al Qaeda on its territory last month after the group's regional off-shoot claimed responsibility for a failed bomb attack on a Detroit-bound plane in December that grabbed the world's attention.

Today, you have attacked us in the middle of our household, so wait for what will befall you in the middle of yours ... We will blow up the earth from beneath your feet, Qasim al-Raymi, the wing's military commander, said in an article posted earlier this month on a website used by Islamist militants.

Yemen said in January it had killed six regional militant leaders in air strikes, but al Qaeda later denied this, and other senior members Sanaa had said were dead, such as deputy leader Saeed al-Shehri, have since re-emerged on websites used by Islamist militants.

In an audio tape posted earlier this month, Shehri, a former inmate of the U.S. prison at Guantanamo Bay, called for a regional holy war and a blockade of the Red Sea to cut off U.S. shipments to Israel.

U.S. intelligence officials say al Qaeda's Yemen wing is emerging as the militant group's most active and sophisticated cell outside the Pakistan-Afghanistan border region.

Defense Secretary Robert Gates has approved more than doubling U.S. funding to train and equip Yemeni security forces to combat al Qaeda, U.S. defense officials said on Monday.

U.S. STRENGTHENS AL QAEDA

In his article, Raymi said U.S. assistance to Yemen has strengthened the militants' popularity among local tribes.

Addressing the U.S. government, he wrote: You united us with our people ... the catastrophe unites those it befalls.

Growing instability in Yemen, the Arab world's poorest country, is a major security concern to the United States and neighboring countries such as the world's top oil exporter Saudi Arabia.

Last week, Sanaa struck a truce with insurgents in the north, who have fought the Sanaa government intermittently since 2004 over religious, economic and social grievances.

Yemen's government has weak control in swaths of the country where the population adheres to tribal structures and laws. It also faces unrest from a southern secessionist movement.

A Yemeni military officer was killed in an ambush in south Yemen on Monday, state media said, following a week of violence after police shot dead a southern protester earlier this month.

The military officer, shot dead in his car, is the third security official killed in southern Yemen in the past week, and the killing follows security sweeps in which authorities seeking to quash strife have arrested around 80 separatists.

Criminal elements of the so-called separatist movement opened fire on Mohamed Abdel-Qader al-Sinhani in an ambush as he returned to his home in the city of Dalea, the Defense Ministry's online newspaper said.

(Additional reporting by Cynthia Johnston; Editing by Dominic Evans)

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