The latest attack occurred at the army's base at Kamra, and the wounded children were taken to a hospital where they were listed in stable condition, Maj. Gen. Waheed Arshad said.
"This barbaric attack shows how cruel the terrorists are," he said, adding that the bus driver and a guard also were injured.
Arshad provided no further details, but an area police official, Mohammed Najam, said the bus belonged to the Pakistan Air Force, and that body parts of the attacker had been collected from scene of the attack, about 50 kilometers (30 miles) northwest of the capital, Islamabad.
Pakistan, a key ally of the United States in its war on terror, has witnessed scores of terrorist attacks that have claimed hundreds of lives in the past several years.
On Sunday, a suicide bomber rammed an explosives-laden car into a police outpost, killing 12 people and wounding several others, in Pakistan's Swat valley, the site of a military operation against Islamic militants loyal to a fugitive cleric, the military said.
The attack occurred after the commander of military operations in Swat said his forces had cleared the valley of insurgents, a military spokesman said.
Militants this summer seized tracts of the area, a former tourist destination about 160 kilometers (100 miles) northwest of Islamabad. On Saturday, the army announced that government troops had retaken all the towns seized by the militants, killing 290 of them and capturing 140.