A roadside bomb exploded near a Pakistan Air Force bus in the volatile North West Frontier Province on Thursday though no one was hurt in the blast.
Suspected militants detonated the device by remote control near Nowshehra, a major city about 120 km northwest of Islamabad that has a large cantonment and several important military facilities, police said.
Three PAF personnel were in the bus when the bomb went off on the main highway between Peshawar and Islamabad.
No group claimed responsibility for the attack. Nowshera has witnessed other attacks on security forces in recent months.
On December 15, a suicide bomber killed at least five people near the gate of an army school in Nowshehra.
Last month, a suicide car bomber wounded five children going to school in a PAF truck near Kamra, about 48 km from Islamabad.
In recent weeks, several suicide attacks have occurred in regions along Pakistan's northwestern border with Afghanistan.
Security forces are conducting a major operation against pro-Taliban militants in the Swat valley of the NWFP.