No group immediately claimed responsibility, though suspicion fell on the Pakistani Taliban who have claimed other recent strikes. The attacks Thursday also were the latest to underscore the growing threat to Punjab, of which Lahore is the capital. The province is next to India where the Taliban are believed to have made inroads and linked up with local insurgent outfits.
President Asif Ali Zardari said the bloodshed that has engulfed the nation over the past two weeks would not deter the government from its mission to eliminate the violent extremists.
"The enemy has started a guerrilla war," Interior Minister Rehman Malik said. "The whole nation should be united against these handful of terrorists, and God willing we will defeat them."
The wave of violence practically shut down daily life in Lahore. All government offices were ordered closed, the roads were nearly empty, and major markets were closed.
The assaults began about 9 a.m. when a single gunman wearing civilian clothes and a suicide vest burst into the offices of the Federal Investigation Agency, the national law enforcement body, and began shooting, said Rana Sanaullah, the provincial law minister. He killed two men and four civilians and was killed by guards at the building before he could detonate his explosives, he said.
Soon after, three or four gunmen raided a police training school on the outskirts of the city, killing 11 officers and recruits, before police killed all the attackers, Sanaullah said. The facility was the scene earlier this year of an eight-hour militant standoff that left 12 dead.
A third team then scaled the back wall of a police commando training center near the airport, Lahore police chief Pervez Rathore said. The attackers stood on the roof of a house, shooting at security forces and throwing grenades, said Lt. Gen. Shafqat Ahmad, the top military officer in Lahore.
The four assailants were killed, along with a police officer and a civilian, Sanaullah said, adding that the gunmen in all three attacks carried dried fruit and apparently were preparing to dig in for a long siege.
The U.S. has trained Pakistani instructors from the center in the past, U.S. embassy spokesman Rick Snelsire confirmed.
Security officials said many of the gunmen were wearing suicide vests and blew themselves up when cornered. Sajjad Bhutta, a senior government official, said the attackers appeared to be both from the lawless tribal regions along the Afghan border and from Punjab.
"They were not here to live. They were here to die. Each time they were injured, they blew themselves up," he said. "They were well trained to the extent they could jump over the walls and shoot well."
TV footage showed helicopters in the air over one of the police facilities and paramilitary forces with rifles and bulletproof vests taking cover behind trees outside the compound's wall.
Officials have warned that Taliban fighters close to the border were increasingly joining forces with Punjabi militants spread out across the country and foreign al-Qaida operatives, dramatically increasing the dangers to Pakistan. Punjab is Pakistan's most populous and powerful province, and the Taliban claimed recently that they were activating cells there and elsewhere in the country for assaults.
An official at the provincial Punjab government's main intelligence agency said they had precise information about expected attacks on security targets and alerted police this week, but the assailants still managed to strike. The official spoke on condition of anonymity because he was not authorized to comment on the situation.
Despite their reach and influence, the nation's feared spy agencies have failed to stop the bloody attacks plaguing the country.
Kamran Bokhari, an analyst with Stratfor, a U.S.-based global intelligence firm, said Pakistan needed to penetrate more militant groups and intercept conversations to prevent attacks, but the task was complicated in a country so big and populous.
"The militants are able to exploit certain things on the ground, like the anti-American sentiment, which is not just in society - it's also in the military," he added.
In the Taliban-riddled northwest, meanwhile, a suicide car bomb exploded next to a police station in Kohat city, collapsing half the building and killing 11 people - three police officers and eight civilians - Kohat police chief Abdullah Khan said.
Early Thursday evening, another bomb exploded in a car outside a housing complex for government employees in the northwestern city of Peshawar, killing a 6-year-old boy and wounding nine others, most of them women and children, said Liaqat Ali Khan, the top police official in the region. He said an assailant parked the car outside the house and walked away before remotely detonating the bomb.
The U.S. has encouraged Pakistan to take strong action against insurgents who are using its soil as a base for attacks in Afghanistan, where U.S. troops are bogged down in an increasingly difficult war. It has carried out a slew of its own missile strikes in Pakistan's lawless tribal belt over the past year, killing several top militants.
One suspected U.S. missile strike killed four people overnight Thursday when it hit a compound in an area in North Waziristan tribal region where members of the militant network led by Jalaluddin Haqqani are believed to operate, two intelligence officials said. They spoke on condition of anonymity because they were not authorized to speak to the media.
Pakistan formally protests the missile strikes as violations of its sovereignty, but many analysts believe it has a secret deal with the U.S. allowing them.
The Taliban have claimed credit for a wave of attacks that began with an Oct. 5 strike on the U.N. food agency in Islamabad and included a siege of the army's headquarters in the garrison city of Rawalpindi that left 23 people dead.
The Taliban have warned Pakistan to stop pursuing them in military operations.
The Pakistani army has given no time frame for its expected offensive in South Waziristan tribal region, but has reportedly already sent two divisions totaling 28,000 men and blockaded the area.
Fearing the looming offensive, about 200,000 people have fled South Waziristan since August, moving in with relatives or renting homes in the Tank and Dera Ismail Khan areas, a local government official said, speaking on condition of anonymity because he was not authorized to talk to the media.
Ahmad reported from Islamabad. Associated Press Writers Rasool Dawar in Mir Ali, Riaz Khan in Peshawar and Zarar Khan and Nahal Toosi in Islamabad contributed to this report.