The improvised explosive device (IED) targeted a convoy of the security forces in Hangu district of Khyber Pakhtunkhwa, Xinhua reported citing officials.
"Six frontier corps soldiers embraced 'shahadat' (martyrdom) due to the IED blast planted by terrorists on the roadside of security forces' convoy in Warmagai area near Hangu," an official said.
Three soldiers died at the scene and 11 others were injured. Three later succumbed to their injuries in a military hospital, officials said.
No group has claimed responsibility for the blast but the authorities suspect that Taliban militants were behind the attack.
Attacks on security forces in Pakistan have increased despite a ceasefire announced by the Taliban Saturday to revive the stalled peace dialogue. The government had also suspended airstrikes against the Taliban in response to the ceasefire.
A government committee formed for talks with the Taliban intermediaries has warned that the attacks could harm the dialogue process.
The committee's members, who met Prime Minister Nawaz Sharif Tuesday, expressed concern at the suicide attack on an Islamabad court which killed 11 people Monday and the recent killings of 15 security men in Khyber tribal region in two attacks.
The Taliban had denied their hand in the Islamabad attack and a lesser known group called Ahrar-ul-Hind had claimed responsibility.
Despite the Taliban denial, the government is asking them to publicly condemn these attacks and help the authorities in exposing those behind these attacks.