Pakistan's regions of Baluchistan, the Federally Administered Tribal Areas (FATA) and North West Frontier Province (NWFP) that border Afghanistan are plagued by violence between militants and government security forces, although the causes of the conflicts differ.

In NWFP, a government offensive against pro-Taliban groups displaced hundreds of thousands of people in April and May 2009.

In semi-autonomous FATA, the army has for years conducted military operations to root out Taliban and al Qaeda militants who fled there after the U.S.-led invasion of Afghanistan in 2001.

In Baluchistan, Pakistan's largest and poorest province, tribal militants are engaged in a long-running, low-level insurgency to gain greater control of the southwestern region's natural resources and political power. Analysts say Afghan Taliban groups are also using Baluchistan as a base.

Islamist militants in the border areas regularly attack NATO supply convoys headed for Afghanistan.

Aid agencies have also come under attack.

Some of the militant violence has spilled into other parts of Pakistan, with suicide and armed attacks on troops and the country's main cities. The nuclear-armed country has also faced years of political violence as it moves between military and civilian rule.

Opposition leader Benazir Bhutto was killed in a suicide attack in December 2007 shortly before a general election.