A suicide bomber killed at least nine police officers and injured several more in Pakistan on Monday.
The police patrol was struck on a bridge in Kachhi, Balochistan province, in a presumed suicide bombing, although the exact nature of the attack has yet to be determined, police superintendent Mahmood Notezai confirmed to Pakistan's Dawn News.
No group immediately claimed responsibility for the attack, in which 13 others were wounded.
It is the latest in a sharp rise in violence that has surged since November, when a ceasefire between the Pakistani Taliban (TTP) and the government ended.
The victims were returning from a week-long cattle show where they had been providing security, Mr Notezai told AFP.
The suicide bomber travelled on a motorcycle and struck the lorry from behind, another police official told the agency.
Attacks are not rare in the south-western province of Balochistan, which lies near the Afghan border and is home to a number of separatist groups waging guerrilla warfare against the government, including the outlawed Balochistan Liberation Army.
Some Baloch groups say federal authorities are exploiting natural resources in the mineral-rich province.
A child was among the victims of a suicide bombing on a police patrol in the provincial capital of Quetta in November, later claimed by the TTP.
The group often targets members of the security forces. It shares a hardline ideology similar to the Afghan Taliban but is a separate organisation.
The TTP called for nationwide attacks after the end of the ceasefire, followed only two months later by a suicide bombing that killed more than 100 people in Peshawar.
Police officers made up most of the victims of that attack, a rare breach of a highly fortified police compound in the city.
Officials admitted a major security lapse had allowed the bomber to gain access to the compound before carrying out the attack in a mosque.
Suicide bomber kills dozens at Pakistan mosque - in pictures
