ISLAMABAD, Pakistan (CNN) -- Residents reported hearing two explosions Monday morning in the Pakistani city of Rawalpindi, which is home to the army's headquarters, police said.
But military officials told CNN that a thorough check of the city and its military installments has revealed nothing out of the ordinary. The sounds, the officials said, may have resulted from something else.
A spokesman for Pakistan's Air Force said it did not have flights scheduled at the time. The sounds, he said, could not have come from its planes breaking the sound barrier -- causing sonic booms that residents may have mistaken for bomb blasts.
Rawalpindi, located about 7 miles (11 km) from the capital city of Islamabad, is a closely guarded city that has experienced several suicide bomb attacks in recent months -- including the recent assassination of Benazir Bhutto.
The government blames the attacks on militants operating out of the country's northwest tribal areas that border Afghanistan.
Reports of the Monday blasts follow a weekend military offensive against the militants in those tribal areas. The militants have vowed revenge for the operation.
On February 25, a suicide bomber detonated explosives near the military headquarters in Rawalpindi, killing at least eight people, including the army's top ranking medical officer.
In early February, a suicide bomber rammed his motorcycle into a van carrying army medics, killing at least four people.
And Bhutto was killed at a rally in the city on December 27 when a bomber blew himself up near her limousine. Videotape showed a gunman firing toward her vehicle as she left the rally.
CNN's Zein Basravi contributed to this report.