A suicide blast on Monday killed one and injured at least 22 others near the Pak-Afghan border at Chaman, security officials said.
A Levies spokesman said the blast targeted a vehicle of the Pakistan Army which was on a routine patrol. Authorities have sealed the border, he added.
No group claimed responsibility for the attack but militant groups, including the Taliban and Islamic State, have carried out such attacks in the past.
Pakistani authorities in March announced they had begun fencing the borders with Afghanistan to prevent incursion by militants, which, according to Islamabad have found sanctuaries in Afghanistan.
The move angered Kabul which has never formally recognised the colonial-era Durand Line border drawn up in 1893.
Prime Minister Shahid Khaqan Abbasi last week had offered “joint patrols" and "joint posts" with Afghanistan as a means of bilateral verification of action taken against terrorist groups or their sanctuaries.
“Whatever it takes to fight terrorism ... Pakistan is totally open to that,” Abbasi said while briefing foreign journalists in Islamabad.