Jan 13 Al Qaeda in the Arabian Peninsula (AQAP) showed its ambition to strike outside its base in Yemen when it claimed the failed Dec. 25 attempt to blow up a U.S. airliner.
Here are some questions and answers about the group:
WHO ARE ITS LEADERS?
AQAP, which emerged a year ago after a merger of al Qaeda's wings in Yemen and Saudi Arabia, is led by Nasser al-Wahayshi, a Yemeni who was once Osama bin Laden's secretary.
Wahayshi and Qasim al-Raymi, who became AQAP's military chief, were among 23 militants who escaped from a Sanaa jail in 2006, enabling al Qaeda to revive its fortunes in Yemen.
U.S.-Yemeni cooperation had led to the killing of al Qaeda's then leader in Yemen, Abu Ali al-Harithi, in a 2002 drone strike and the arrest of his successor Mohammed Hamdi al-Ahdal in 2003.
Several Saudi militants have joined the group in Yemen, notably its deputy leader, Saeed al-Shehri, who is a former inmate at the U.S. prison at Guantanamo Bay, Cuba.
Yemeni officials say AQAP has no more than 300 militants, but it may have many more sympathisers in a land where anti-U.S. sentiment is rife. AQAP has sought to forge links with restive tribes in areas where government control is already weak.
WHAT DOES IT WANT?
AQAP espouses a militant Sunni Islamist ideology that makes violent jihad an obligation for all Muslims.
It has threatened attacks on Westerners to cleanse the Arabian peninsula of "infidels" and seeks the fall of the U.S.-allied royal family in oil superpower Saudi Arabia.
AQAP also wants to weaken or destroy President Ali Abdullah Saleh's government to create safe havens in Yemen from which to launch attacks anywhere from Saudi Arabia to the United States.
It represents a new generation of militants who take a harsher line against Sanaa than their predecessors, who sometimes did deals with the government.
Many Yemenis fought against the Soviet army in Afghanistan in the 1980s, and later in Bosnia, Chechnya, Kashmir and Iraq.
WHAT HAS IT ACHIEVED?
AQAP claimed a suicide bombing that killed four South Korean tourists in March in Yemen's eastern province of Hadramaut.
In August, it sent a suicide bomber posing as a repentant militant to Saudi Arabia, where he narrowly failed to kill the kingdom's anti-terrorism chief Prince Mohammed bin Nayef.
Two AQAP militants were killed in a shootout with Saudi police in October after driving across the border from Yemen on what analysts say was an apparent suicide mission. AQAP said it was behind the alleged attempt by Umar Farouk Abdulmutallab, a Nigerian, to blow up a Detroit-bound U.S. airliner on Dec. 25 using explosives sewn into his underwear.
The group killed two Belgian women and two Yemeni drivers in January 2008 and carried out a twin suicide bombing of the U.S. embassy in September that year, killing 16 people.
Al Qaeda also bombed the USS Cole in Aden harbour in 2000, killing 17 sailors. Two years later an al Qaeda attack damaged the French supertanker Limburg in the Gulf of Aden.
WHAT MIGHT IT TARGET NEXT?
Nobody knows, but AQAP has shown itself to be innovative and keen to carry out spectacular attacks.
Saudi Arabia, which in 2006 eventually crushed an al Qaeda armed campaign, is likely to remain firmly in AQAP's sights.
The United States is another priority target for AQAP, especially as it ramps up support for Yemeni government forces and encourages them to hunt and destroy the militants.
Britain could also be targeted. It plans to host a Jan. 28 conference on how to counter militancy in Yemen and Afghanistan in an initiative denounced by a radical Yemeni cleric.
Yemen's oil and gas facilities, particularly pipelines, and the offices of Western companies operating in the country are among other possible AQAP targets, analysts say.
AQAP could try to attack ships in the Gulf of Aden, where Somali pirates already prey on one of the world's busiest sea lanes, perhaps using suicide bombers in small boats as before.
A leader of Somalia's al Qaeda-inspired al Shabaab force offered this month to send fighters across the Gulf of Aden to help AQAP if the United States attacked its bases in Yemen.
WHAT COUNTER-MEASURES DOES IT FACE?
Yemen stepped up raids on suspected AQAP hideouts with U.S. support shortly before the Dec. 25 airliner attack. It said 60 militants were killed in air strikes and security sweeps, including Wahayshi, Shehri and U.S.-Yemeni Internet preacher Anwar al-Awlaki. None of the deaths has been confirmed.
The United States has said it will not send ground troops to Yemen, but plans to increase its security assistance to at least $150 million this year from $70 million in 2009.
Yemeni forces have been receiving more U.S. support to help them fight AQAP, but much of the military aid has been covert, partly to avert a public backlash against the Yemeni government.