The incident in Bajaur tribal region on Friday came days after Pakistan lodged a strong protest with US-led forces in Afghanistan, saying cross-border firing in the nearby Waziristan area last weekend killed eight people.
A resident of Bajaur, which borders Afghanistan's insurgent-troubled Kunar province, said the explosions were caused by firing from unidentified aircraft on the village of Damadola.
Shah Jehan, a shopkeeper who lives about 2km from the village, said: "According to our information, 18 people have been killed."
Major-General Shaukat Sultan, the military spokesman, said he did not know the cause of the blasts, but said: "People heard explosions and as a result there were a number of casualties. My information is that 11 to 14 people have been killed."
A Pakistani intelligence official said two aircraft had come in from Afghanistan and fired two or three missiles.
"The casualties may be much higher. People are very angry. They are not allowing access, so exact figures of deaths and wounded people are not available," he said.
Lieutenant-Colonel Jerry O'Hara, a US military spokesman in Afghanistan, said there were no reports of US forces operating in the Damadola area.
Nearby Waziristan has been the scene of clashes between security forces and al-Qaida militants for more than two years, but there have been no previous reports of fighting in Bajaur.
On Monday, Pakistan lodged a strong protest with US-led forces in Afghanistan, saying cross-border firing in the Mir Ali area of Waziristan the previous Saturday had killed eight people, including a woman, and wounded nine.
"The casualties may be much higher. People are very angry. They are not allowing access, so exact figures of deaths and wounded people are not available"
Pakistani intelligence official
In separate violence, suspected separatist militants in the troubled southwestern province of Baluchistan fired rockets into an army camp killing three soldiers, an official said.
A provincial official said the militants fired up to 10 rockets late on Thursday on the camp in Margat, a coal-mining area 100km east of the provincial capital, Quetta.
Baluch militants have been waging a low-level insurgency for decades in pursuit of greater benefits and control of gas and other natural resources, but they have intensified their campaign in recent months.