Orakzai is one of seven ethnic Pashtun tribal areas where the Pakistani army has tried to root out militants with offensives against their strongholds.
The strike came a day after a local newspaper reported that Pakistan will launch an offensive in North Waziristan, a known sanctuary for al Qaeda and Taliban militants also located in Pakistan's tribal belt.
Pakistan's performance in fighting militancy has come under close scrutiny again after it was discovered that al Qaeda chief Osama bin Laden had been living in the country.
Army operations in areas like Orakzai have failed to break the back of militant groups such as the Pakistani Taliban, who have stepped up suicide bombings since U.S. special forces killed bin Laden near Islamabad on May 2.
"We had information that militants gathered there and were planning attacks so we launched the attack," a local senior government official told Reuters. He said 17 militants were killed and six wounded in the Orakzai operation.
U.S. PRESSURE
Residents in the town of Mamoozai, where the air strike took place, said several helicopter gunships were hovering overhead hours after the attack.
After the bin Laden raid, the United States told Pakistan it needs to step up the fight against militants, and government officials said Mamoozai has become a hub for militants who fled military operations elsewhere in the tribal belt, a strategy that has enabled them to survive army assaults.
The Pakistani Taliban, which has strong ties to al Qaeda, has attacked army recruits, a naval base, and trucks carrying fuel to U.S.-led NATO troops in Afghanistan to avenge the death of bin Laden.
On Tuesday, gunmen on a motorcycle attacked and torched two NATO trucks in southwestern Baluchistan province, a provincial government official said.