The attack hit the outskirts of Darra Adam Khel, a town about 25 kilometres (15 miles) south of Peshawar, the capital of the North West Frontier Province, where security forces are locked in heavy fighting with Taliban further north.
"One security personnel and five civilians were killed while three were wounded when a suicide bomber exploded his car near a security checkpost," said a military official in the region who did not want to be named.
The bomb site and a nearby tunnel have been sealed off, while the injured were rushed to hospital, he added.
A local administrative official confirmed the attack.
No one claimed responsibility for the blast, but Pakistan security forces are a frequent bombing target for Islamist militants.
Troops have fought increasingly fierce battles against Taliban militants in the northwest and across a semi-autonomous tribal belt.
The area became a safe haven for Al-Qaeda and Taliban extremists who fled the US-led invasion to oust the hardline Taliban regime from neighbouring Afghanistan in late 2001.
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