TIMELINE: Militant attacks in Pakistan

(Reuters) - Gunmen attacked a police headquarters in the Pakistani city of Lahore on Wednesday, opening fire and setting off a car-bomb that killed 22 people and wounded nearly 300.

There was no claim of responsibility but the blast comes as the army battles militants in the Swat region of the country's northwest in its most concerted action to push back a growing Taliban insurgency.

Militant violence has surged in nuclear-armed Pakistan in recent years, with numerous attacks on security forces and government and Western targets.

Following is a timeline of major attacks in 2009:

May 16, 2008 - Car packed with mortar bombs blows up in the northwestern city of Peshawar, killing 11 people, including four children passing in a school bus.

May 11 - Ten people are killed and more than a dozen wounded in a suicide car bomb attack on a security checkpost near Peshawar.

April 25 - Twelve children who mistake a bomb for a toy are killed when it explodes as they play with it in the Low Dir district near Swat. Authorities say it is unclear whether the incident is an "act of terrorism" or an accident.

April 18 - A suicide car-bomber rams a military convoy, killing 25 soldiers and police and two passers-by near Kohat, 190 km (120 miles) west of Islamabad.

April 15 - A suicide car-bomber blows himself up at a security post in the northwest, killing nine policemen and three civilians.

April 5 - A suicide bomber blows himself up in a religious center for minority Shi'ite Muslims in Chakwal in central Pakistan. At least 17 people are killed and about 11 seriously wounded. The attack comes a day after a suicide attack in Islamabad killed eight paramilitary soldiers.

March 30 - Militants armed with guns and grenades storm a police training center in Lahore killing eight recruits, wounding scores and holding off police and troops for eight hours. The attack is claimed by Pakistani Taliban leader Baitullah Mehsud. Four militants are killed and three arrested.

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

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

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 town.

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