A roadside bomb exploded near a bus carrying security forces in restive southwestern Pakistan on Sunday, killing at least five officers and wounding 10 others, police said.
The attack occurred in Naushki, a district in Balochistan, said Zafar Zamanani, a local police chief.
He said the the blast also badly damaged another nearby bus. The dead and wounded were transported to a nearby hospital.
"There were seven buses in the convoy which was heading to Taftan (on the Iranian border). At Noshki, a car laden with explosives hit one of the buses," Zafar said.
Sarfraz Bugti, the chief minister of Balochistan, condemned the attack.
Meanwhile, the Baloch Liberation Army (BLA) claimed responsibility for the attack, alleging 90 personnel were killed.
In a statement, the group said its Majeed Brigade carried out a vehicle-borne suicide bombing on a convoy traveling along the RCD Highway near Rakhshan Mill.
One of the eight buses was completely destroyed in the blast, it added.
The group further claimed its fighters later surrounded another bus and killed all personnel on board.
The total number of casualties could not be independently verified.
The attack is part of a series of escalations by the outlawed BLA, which days ago hijacked a train carrying about 400 passengers.
The militants killed nearly 30 hostages before security forces launched a counter offensive, killing all 33 attackers.
Oil-and mineral-rich Balochistan is Pakistan's largest and least populated province. Ethnic Baloch residents have long accused the central government of discrimination, a charge Islamabad denies.
Baloch Liberation Army has been demanding independence from the central government.