FACTBOX: Militants groups in Pakistan's Punjab province

(Reuters) - Pakistani commandos stormed an office building on Sunday and rescued 39 people held hostage by Islamist militants after a brazen attack on the headquarters of the army. The 22-hour-long drama ended with the capture of a hostage-taker who was wounded while blasting the explosives before his arrest. The military identified the arrested militant as Aqeel, alias Dr. Usman, and said he was the "ringleader."

Security officials said he was believed to be a member of the Lashkar-e-Jhangvi, an al Qaeda-linked grouped based in the central province of Punjab.

Here are some facts about some of the major groups in Punjab, Pakistan's biggest province.

LASHKAR-E-JHANGVI

Sunni Muslim Lashkar-e-Jhangvi (LeJ) is one of the most notorious al Qaeda-linked groups with roots in Punjab. It also has forged strong ties with the Pakistani Taliban groups operating in the tribal areas on the Afghan border.

A senior leader of LeJ, Qari Muhammad Zafar, appeared before a group of journalists in the militant stronghold of South Waziristan tribal region last week along with new Pakistani Taliban chief, Hakimullah Mehsud.

Zafar carries a $5 million reward from the United States on his head for his suspected involvement in a bomb attack on the U.S. consulate in the southern city of Karachi.

LeJ emerged as a sectarian group in the 1990s targeting minority Shi'ite Muslims but later graduated to more audacious attacks, such as the truck bombing of Islamabad's Marriott Hotel last year in which 55 people were killed as well as an assault on a Sri Lankan cricket team in which seven Pakistanis were killed. Six members of the team and a British coach were wounded.

LeJ was outlawed in Pakistan in August 2001. LeJ members are also involved in violence in Afghanistan.

A security official told Reuters about two dozen militants linked to LeJ and two other militant groups, Sipah-e-Sahaba Pakistan and a splinter faction of Jaish-e-Mohammad, were suspected to be behind several Punjab attacks in recent months.

SIPAH-E-SAHABA PAKISTAN (SSP)

SSP is a pro-Taliban anti-Shi'ite militant group based in central Punjab. The group was banned in 2002 but officials say its members were suspected of involvement in attacks in the province in recent months, including the burning to death of seven Christians on suspicions of blasphemy.

JAISH-E-MOHAMMAD

Jaish-e-Mohammad, or army of the Prophet Mohammad, is a major militant group with links to the Taliban and al Qaeda. It was banned in Pakistan in 2002 after it was blamed for an attack on the Indian parliament in December 2001.

The group was founded by firebrand cleric Maulana Azhar Masood shortly after his release from an Indian jail in exchange for 155 passengers of an Indian airliner hijacked to the southern Afghan city of Kandahar in December 1999.

The group focused its fighting on the Indian part of divided Kashmir but later forged links with al Qaeda and the Taliban and was suspected of involvement in several high profile attacks including the murder of U.S. journalist Daniel Pearl in 2002 and an assassination attempt on former president Pervez Musharraf.

Rashid Rauf, a British militant suspected of being ringleader of a 2006 plot to blow up airliners over the Atlantic, was also a Jaish member. Masood was arrested by Pakistani authorities shortly after the group was banned but security officials say he has disappeared since 2005.

Jaish fighters are also involved in violence in northwest Pakistan and across the border in Afghanistan.

LASHKAR-E-TAIBA

Lashkar-e-Taiba (LeT), or the army of Taiba. Taiba is the old name of the Muslim holy city of Medina in Saudi Arabia. The group was founded in 1990 to fight Indian rule in Kashmir. It was blamed for the coordinated attacks on the Indian financial capital, Mumbai, in November last year that killed 166 people. LeT was also blamed for the late 2001 Indian parliament attack and was also banned in Pakistan in 2002.

Seven LeT-linked militants are being tried in Pakistan for suspected involvement in the Mumbai assault but India is insisting Pakistan prosecute its founder, Hafiz Mohammad Saeed, who India says was the attack mastermind.

A U.N. Security Council committee last year added Jamaat-ud-Dawa, a charity headed by Saeed, to a list of people and organisations linked to al Qaeda and the Taliban.

(Editing by Robert Birsel and Jerry Norton)