Yemen has stepped up a campaign to root out al Qaeda militants after the group's Yemen-based wing said it was behind a December 25 attempt to bomb a U.S. airliner.

Here is a timeline tracing al Qaeda activity in Yemen since 2000:

Oct 12, 2000 - Bombing of USS Cole in Aden harbour kills 17 sailors and blows hole in navy vessel's hull. Oct 6, 2002 - Explosion damages French supertanker Limburg in Gulf of Aden in attack for which five al Qaeda-linked Yemenis are later convicted.

July 2, 2007 - Seven Spanish tourists are killed when car bomb hits their convoy in eastern province of Marib.

March 17, 2008 - Three mortar rounds miss U.S. embassy in Sanaa and hit girls school, killing school guard.

Aug 11, 2008 - Five al Qaeda suspects are killed and two arrested after police storm hideout in southern town. Yemen links them to attacks on Spanish tourists and U.S. embassy.

Jan 18, 2008 - Gunmen fire on tourist group in Hadramaut, killing two Belgian women and their two Yemeni drivers.

Sept 17, 2008 - Two suicide car bombers attack heavily fortified U.S. embassy complex in Sanaa, killing 16 people. Washington says attack bore all the hallmarks of al Qaeda.

Jan 2009 - Al Qaeda's Yemeni and Saudi wings announce merger in new group called al Qaeda in the Arabian Peninsula (AQAP) led by Nasser al-Wahayshi, former Yemeni aide to Osama bin Laden.

June 2009 - Bodies of three kidnapped foreign women -- two Germans and a South Korean -- are found in northern province of Saada. Six other foreigners remain missing. No group claims responsibility. AQAP is among suspects.
Aug 27, 2009 - Abdullah al-Asiri, an al Qaeda suicide bomber posing as repentant militant, is flown from Yemen to Saudi Arabia, where he tries to kill kingdom's anti-terrorism chief Prince Mohammed bin Nayef in first such attack on a Saudi royal.

Nov 3, 2009 - Al Qaeda claims killing of seven Yemeni security officials in ambush near Saudi border.

Dec 17, 2009 - Yemen says 30 al Qaeda militants are killed and 17 arrested in air raids and security sweeps in southern province of Abyan and Arhab district northeast of Sanaa.

Dec 24, 2009 - Yemen says 30 al Qaeda militants are killed in air strikes in eastern province of Shabwa. Security official says Wahayshi, his Saudi deputy Saeed al-Shehri and U.S.-born cleric Anwar al-Awlaki are among dead. There is no confirmation.

Dec 28, 2009 - AQAP claims responsibility for failed bombing of Detroit-bound U.S. airliner three days earlier.

(Writing by David Cutler, London Editorial Reference Unit; Editing by Alistair Lyon)

Terrorism