Pakistani authorities seized nearly 14 tonnes of potassium chlorate, a key ingredient in bomb-making, from a bus in the country’s violent and unstable southwest on Sunday.

Pakistani authorities seized nearly 14 tonnes of potassium chlorate, a key ingredient in bomb-making, from a bus in the country's violent and unstable southwest on Sunday, officials said.

The haul was made when officials acting on a tip-off stopped a bus just outside the city of Quetta loaded with the volatile substance hidden under cartons of food, an official with the government paramilitary force said.

"We have seized some 13,900 kilograms of potassium chlorate from a bus and arrested five people," Frontier Corps Captain Johar Sarwar told Agence France Presse.

"The substance was hidden in sacks under various food items."

The bus was bound for the remote town of Naushki, around 110 kilometers (65 miles) west of Quetta, he said, adding that bomb disposal officers were summoned to check for detonators, but they found none.

Baluchistan province, of which Quetta is the capital, is frequently hit by bomb attacks.

The oil and gas-rich area borders Iran and Afghanistan, and suffers attacks by Taliban militants and a tribal insurgency.