The coastguards’ vehicle hit the explosives in Koldan town, near the Iranian border and some 80 kilometres (47 miles) from Gwadar, a seaport managed by Beijing.
“The coastguards’ vehicle was part of a convoy which brings drinking water for them from Koldan town to the port of Gwadar daily,” said Muhammad Anwar, a senior administration official in the area.
“Five guards were injured when their vehicle hit the landmine and two of them succumbed to their injuries later,” he said.
Another government official confirmed the incident and causalities.
Gwadar port is being developed under Beijing’s ambitious $46 billion infrastructure plan called the China Pakistan Economic Corridor, to link China’s western city of Kashgar to the Pakistani port of Gwadar on the Arabian Sea.
The corridor plans have been strongly criticised by New Delhi, with India’s Foreign Minister Sushma Swaraj last year calling the project “unacceptable” for crossing through Indian-claimed territory — Pakistan’s northern Gilgit-Baltistan region which is attached to the disputed territory of Kashmir.
Pakistan’s Balochistan province, of which Gwadar is a part, is rife with separatist, Islamist extremist and sectarian violence.
The mineral-rich province has long been targeted by militants, and Islamabad accuses New Delhi of fuelling unrest in the region to hamper Pakistan’s development.
A spokesman for the separatist Baloch Liberation Army (BLA) told AFP that they claimed responsibility for the blast.
“We claim responsibility for this attack in Koldan. We will continue targeting Pakistani forces,” Meerak Baloch said.