ISLAMABAD - A suicide bomber rammed a car packed with explosives into a school bus near an air force base in northwestern Pakistan on Monday, killing himself and wounding about nine people, including several children, the military said.

"A terrorist targeted a schoolchildren's bus. The driver and the guard who were sitting in the front have been seriously injured," said military spokesman Major-General Waheed Arshad.

"Because of the timely reaction of the driver, the children were saved. Only about six or seven children were injured," he added. "It was outside the Kamra air base. It was specially targeting the schoolchildren's bus."

He said the wounded children had been taken to a nearby hospital. The base is about 45 miles northwest of the capital, Islamabad.

The attack came a day after a suicide bomber rammed a car packed with explosives into a police checkpost in the Swat valley in the northwest, killing six people. The military reimposed a curfew in seven towns in the area following the attack.

The army launched a major offensive last month to drive insurgents led by a pro-Taliban cleric out of the Swat area, where they are striving to impose strict Islamic code.

The military says the militants have fled into remote valleys to the northwest after 290 of them were killed and nearly 150 captured in the offensive.

There have been a rash of suicide attacks blamed on Islamist militants since a military assault on the Red Mosque, a militant stronghold, in Islamabad in July.

More than 800 people have been killed in ensuing violence across the country since then, about half of those killed in suicide attacks.

President Pervez Musharraf, a key ally in the U.S.-led war on terrorism, cited growing militancy as a main reasons behind his imposition of emergency rule by him on November 3.

Critics say he was more focused on safeguarding his re-election from legal challenges.