TIMELINE: Attacks destabilize strife-torn Pakistan

(Reuters) - Militants holed up in a police training center in the Pakistani city of Lahore on Monday after storming the complex and killing cadets, with estimates of the dead ranging up to 20.

Militant violence has surged in nuclear-armed Pakistan since mid-2007, with numerous attacks on security forces and government and Western targets. Following is a timeline of major attacks in Pakistan since late 2007:

October 19, 2007 - At least 139 people are killed in a suicide bomb attack on former prime minister Benazir Bhutto's motorcade as she is driven through the financial capital of Karachi at the end of eight years of exile. She was unhurt.

December 21 - A suicide bomber kills at least 41 people in a mosque in Charsadda district, in the North West Frontier Province (NWFP), during the Muslim Eid festival prayers.

December 27 - Bhutto is killed in a gun and bomb attack after a rally in northern garrison town of Rawalpindi. At least 16 others are killed.

February 29, 2008 - A suicide attack on a police funeral kills 40 people in the turbulent northwestern district of Swat, 160 km (100 miles) from Pakistan's capital, Islamabad.

March 2 - At least 40 people are killed as suicide bomber attacks gathering of tribal elders in Darra Adam Khel, a northwestern tribal region.

March 11 - Two suicide car bombers kill 24, most of them in an attack on a government security office in the country's second largest city, Lahore, near the Pakistan-India border.

March 15 - A bomb attack at an Italian restaurant in Islamabad, a favorite hangout for foreigners, kills a Turkish woman and wounds several others, including four FBI agents.

August 19 - Suspected suicide bomber kills 23 in compound of hospital in Dera Ismail Khan in the NWFP, southwest of Islamabad, as Shi'ite Muslims protest a leader's killing.

August 21 - Two suicide bombers blow themselves up outside the main defense industry complex in Wah, 30 km (18 miles) northwest of Islamabad. Nearly 50 people are killed and about 70 wounded.

September 20 - Suicide truck bomb attack blamed on Islamist militants kills 55 people, destroys Marriott hotel in Islamabad.

December 5 - A car bomb kills at least 20 people and wounds scores in Peshawar, capital of NWFP.

December 28 - At least 30 people are killed in a suicide car bomb blast at a polling station near Buner, in the NWFP, during a by-election for a provincial assembly.

February 5, 2009 - At least 24 people are killed in a suspected suicide bombing near Shi'ite mosque in Dera Ghazi Khan, central Pakistan.

February 20 - Suicide bomber kills 27 people and wounds 65 in an attack on a funeral procession for a Shi'ite Muslim killed a day earlier in Dera Ismail Khan.

March 3 - Gunmen attack a bus carrying Sri Lanka's cricket team outside a Lahore stadium, killing seven people, including six policemen, and wounding six of the cricketers and a British coach.

March 7 - Eight Pakistani police and soldiers are killed in a booby-trapped car bomb attack on a police van on the outskirts of the northwestern city of Peshawar.

March 16 - A bomb explodes near a bus stop in Rawalpindi, killing seven people.

March 27 - A suicide bomber kills 37 people when he blows himself up in a crowded Pakistani mosque near the Afghan border. Among the dead are 14 policemen and paramilitary soldiers.

March 30 - Militants armed with guns and grenades storm a police training center in Lahore.