The blast took place at Katasarai village in restive Kurram tribal district bordering Afghanistan where Pakistani army and paramilitary forces have launched an operation against Taliban militants.
“Three security personnel including a lieutenant have embraced martyrdom and one other was wounded in an IED (improvised explosive device) blast,” a senior security official told AFP.
Local intelligence officials suspect the involvement of Taliban militants in the attack.
Pakistan has for years battled homegrown insurgents in the tribal belt that borders Afghanistan.
More than 3,000 soldiers have died but Pakistan has resisted US pressure to do more to eliminate havens used by Afghan insurgents.
On Thursday, the US Senate voted to freeze roughly $700 million in aid to Pakistan pending assurances from Islamabad on taking steps to thwart militants who use improvised explosive devices (IEDs) against US-led forces in Afghanistan.
Pakistan angrily criticised the move, the latest rift in a fraying alliance that has been in deep crisis since air strikes by US-led forces killed 24 Pakistani soldiers last month.
