Teams of gunmen attacked three security sites Thursday in the eastern Pakistani city of Lahore while a suicide bomber hit a northwestern town, killing a total of 37 people. The strikes were part of an escalating a wave of terror aimed at scuttling a planned offensive into the militant heartland on the Afghan border. One of the attacks, on a commando training facility on Lahore's outskirts, lasted into Thursday afternoon, before security forces killed the five attackers and freed a family they were holding hostage, police said. The assaults paralyzed the cultural capital of this nuclear-armed US ally, showing the militants are highly organized and able to carry out sophisticated, coordinated strikes against heavily fortified facilities despite stepped up security across the country. No group immediately claimed responsibility, though suspicion fell on the Taliban who have claimed other recent strikes. The attacks Thursday also were the latest to underscore the growing threat to Punjab, the province 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 11 days would not deter the government from its mission to eliminate the violent extremists, according to a statement on the state-run news agency. "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 halted activity in Lahore. All government offices were ordered shut, the roads were nearly empty, major markets did not open and stores that had been open pulled down their shutters. The violence began just after 9 a.m. when a group of gunmen attacked a building housing the Federal Investigation Agency, a law enforcement branch that deals with matters ranging from immigration to terrorism. "We are under attack," said Mohammad Riaz, an FIA employee reached inside the building via phone by The Associated Press during the assault. "I can see two people hit, but I do not know who they are." The attack lasted about 1 1/2 hours and ended with the death of two attackers, four government employees and a bystander, senior government official Sajjad Bhutta said. Senior police official Chaudhry Shafiq said one of the dead wore a jacket bearing explosives. Soon after that assault began, a second band of gunman raided a police training school in Manawan on the outskirts of the city in a brief attack that killed nine police officers and four militants, according to police and hospital officials. One of the gunmen was killed by police at the compound and the other three blew themselves up. The facility was hit earlier this year in an attack that sparked an eight-hour standoff with the army that left 12 people dead. A third team of at least eight gunmen scaled the back wall of an elite police commando training center not far from the airport and attacked the facility, Lahore police chief Pervez Rathore said. Senior police official Malik Iqbal said at least one police constable was killed there. Lt. Gen. Shafqat Ahmad said five attackers were slain in a gunbattle and suicide blasts in the facility, and Shafiq said security forces freed a family that was being held hostage at the compound. Television 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 a wall surrounding the compound. Rana Sanaullah, provincial law minister of Punjab province, said police were trying to take some of the attackers alive so they could get information from them about their militant networks. Officials have warned that Taliban fighters close to the border, Punjabi militants spread out across the country and foreign al-Qaida operatives were increasingly joining forces, 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. In the Taliban-riddled northwest, meanwhile, a suicide car bomb exploded next to a police station in the Saddar area of Kohat, collapsing half the building and killing 11 people - three police officers and eight civilians - Kohat police chief Abdullah Khan said. The US has encouraged Pakistan to take strong action against insurgents who are using its soil as a base for attacks in Afghanistan, where US 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 including Pakistani Taliban chief Baitullah Mehsud. One suspected US 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 US allowing them. The militants have claimed credit for a wave of attacks that began with an Oct. 5 strike on the UN 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.