BANNU, Pakistan (AP) -- Pakistani jets pounded targets in the country's northwest on Monday as the military suffered its first casualties in a major offensive designed to root out safe havens in the volatile region.
The airstrikes are part of a long-awaited operation against foreign and local militants in North Waziristan, an essentially lawless tribal region which has served as a training base for militants and a staging point for insurgents who attack Pakistan and NATO and Afghan troops across the border. The operation started Sunday.
The United States has for years complained to Pakistan about its failure to impose order in a region harboring what Washington considers the country's most dangerous militants, and has carried out hundreds of drone strikes in the area.
The offensive marks the end of the government's policy of trying to negotiate with Pakistani Taliban militants instead of using force to end years of fighting which has killed tens of thousands of civilians and security forces.
Prime Minister Nawaz Sharif, who has promoted the talks, defended military action during a speech to parliament on Monday. Sharif said the government had tried for more than four months to talk to the militants but their violence continued. He said Pakistan could not become a safe haven for militants.
In Washington, State Department spokeswoman Jen Psaki said the U.S. has long supported Pakistani efforts to extend sovereignty throughout the country and bring stability, but she emphasized this was an "entirely Pakistan led and executed operation."
She declined to comment on whether the operation would help U.S. efforts in Afghanistan.
The airstrikes early Monday targeted six hideouts near the border with South Waziristan, a neighboring tribal region, killing 27 militants, the military said.
Separately, the military said 14 militants were killed in separate confrontations while another three were shot trying to lay roadside bombs near Miran Shah, one of the region's main towns. Altogether the military reported that nearly 200 militants had been killed during the two-day offensive.
The military said eight troops died Monday -- six by a roadside bomb and two during a shootout with militants -- as the Pakistani Taliban warned that more violence could be in the offing.
A spokesman for the militants warned in a statement sent to reporters that international investors, foreign airlines and multinational organizations should leave Pakistan or they'd be considered supporters of the government and fair game.
Shahidullah Shahid also vowed to retaliate in the cities of Islamabad and Lahore, cities that have largely been spared the bombings and shootings that plague places like Karachi and Peshawar.
Security was being stepped up across Pakistan. In Karachi, armored personnel carriers could be seen rolling out the gates of a military base. The military said they were being used to protect sensitive installations.
Few details have been released about the size of the operation or the military assets involved.
The military said troops were sealing off the North Waziristan borders and the main cities, ensuring the evacuation of civilians in addition to establishing areas where militants can surrender their weapons. The military said no operations had yet been launched in civilian areas.
Residents reached by telephone reported hearing loud explosions overnight but said they cannot go outside because there is a curfew in place.
"We have been just hearing big bangs and explosions. We can't go out to see what's happening out there," Sajid Dawar, a resident of Miran Shah, said by telephone.
Another resident, Ziaullah Khan from Mir Ali, said people were starting to run out of food because the markets had been closed for a few days.
North Waziristan is one of the last parts of the tribal regions where the military has not launched a large operation. Militant groups including the Pakistani Taliban, al-Qaida and the Haqqani network have long used the region as a base.
The Pakistani military said it has asked the Afghan government for help reinforcing its side of the border, to prevent militants from fleeing. Afghanistan and Pakistan have long accused each other of failing to act against insurgents.
Critics say Pakistan maintains a so-called "good Taliban, bad Taliban" policy in which it combats the Pakistani Taliban, who attack the state, but tolerates or supports the Afghan Taliban in order to maintain influence in the neighboring country.
The offensive comes a week after militants laid siege to Pakistan's largest airport in an attack that shocked the country and appeared to mark a turning point in the government's thinking about military action.
But the large military operation could spark a wave of bloody reprisal attacks, especially in Karachi or Peshawar, where militants already have a sizeable presence.