(Reuters) - Pakistani security forces are battling Taliban militants in their Swat valley bastion just 130 km (80 miles) northwest of Islamabad after a pact aimed at ending violence in the region collapsed.
Prime Minister Yusuf Raza Gilani had said in a televised address late on Thursday that extremists were trying to hold the country hostage at gunpoint, and ordered the military "to eliminate the militants and terrorists."
Surging violence and spreading Taliban influence have sent jitters across Pakistan and compounded Washington's worries about the stability of its nuclear-armed ally, vital for efforts to defeat al Qaeda and stabilize neighboring Afghanistan.
Here are few facts about Pakistani Taliban.
WHO ARE THE PAKISTANI TALIBAN?
Most Pakistani Taliban fighters are ethnic Pashtuns from northwestern regions on the Afghan border. They support the Afghan Taliban, most of whom are also Pashtun and many of whom fled to the Pakistani Pashtun lands after U.S.-led forces ousted Afghanistan's Taliban government in late 2001.
Thirteen factions based in different parts of northwest Pakistan have formed a loose umbrella group, the Tehrik-e-Taliban Pakistan (TTP), or Taliban Movement of Pakistan, led by Baitullah Mehsud, based in South Waziristan on the Afghan border.
The United States in March announced a reward of $5 million for information leading to Mehsud's location or arrest.
Mehsud has been accused by Pakistani officials of being behind a wave of suicide attacks across Pakistan since the army stormed Islamabad's Red Mosque in July 2007 to crush a militant movement based there.
But it was when government officials named Mehsud as the prime suspect in the assassination of former prime minister Benazir Bhutto in a gun and bomb attack in the city of Rawalpindi in December 2007 that Mehsud's notoriety rocketed.
The Taliban fighting in Swat are part of the TTP and are led by a commander called Fazlullah, the son-in-law of a pro-Taliban cleric who led thousands of tribesmen to Afghanistan to fight alongside Taliban after the U.S. invasion in 2001.
While many senior Taliban are veterans of Afghan fighting, they have been able to exploit poverty, frustration over an ineffective judiciary, anger against landlords and widespread anti-U.S. feelings to attract recruits. Intelligence officials say they also press families to send sons to fight.
ARE THE PAKISTANI TALIBAN LINKED TO AL QAEDA?
Intelligence officials and security experts say Mehsud is an al Qaeda ally. He has given refuge to a large number of foreign militants, including Arabs and Central Asians, but the nature of his links with al Qaeda's leaders, believed to be hiding along the Afghan-Pakistani border, is not clear.
WHAT IS THE RELATIONSHIP WITH THE AFGHAN TALIBAN?
The TTP swears allegiance to Mullah Omar, chief of the Taliban movement in Afghanistan, and acknowledges sending fighters across the border to Afghanistan where they aim to fight and expel what they call Western "occupation" forces.
However, there are differences between the groups on whether to fight Pakistani security forces. Some groups oppose violence in Pakistan and want all Taliban to focus on fighting in Afghanistan.
However, groups such as those headed by Mehsud and Fazlullah argue that fighting Pakistani security forces is justified because of Pakistan's support for the U.S.-led campaign against al Qaeda and the Afghan Taliban.
Militant groups focused on fighting in Afghanistan recently set up the Ittehad-e-Shura-e-Mujahideen, or Union of the Consultative Council of Mujahideen, with the TTP. Analysts saw the move as aimed at forging unity among all factions in the face of a sharp build-up of U.S. forces in Afghanistan.
ANY LINKS WITH OTHER MILITANT GROUPS?
Intelligence officials say the Pakistani Taliban have also forged links with militants groups mainly drawn from central Punjab province, giving the militants the ability to expand their influence out of the Pashtun-dominated northwest. One of these groups, the Lashkar-e-Jhangvi (LeJ), a Sunni Muslim militant group, is regarded as one of al Qaeda's main fronts in Pakistan. The LeJ specializes in targeting minority Shi'ite Muslims but graduated to high-profile attacks. It is suspected of organizing a suicide truck bombing of Islamabad's Marriott Hotel last year that killed 55 people.
The Pakistani Taliban are also believed to have forged links with the Jaish-e-Mohammad group, which has focused on fighting Indian rule in Kashmir.