The attack in the heart of a city which was recently handed over to Afghan security forces was a reminder of the Taliban's reach; even at a time of stepped up pressure from US and Afghan troops.
(Read: "Afghanistan and the US troops’ withdrawal")
The explosion happened near the police chief's compound in the provincial capital and appeared to target a joint Afghan police and army patrol.
The Ministry of Interior condemned the attack and in a statement described it as "un-Islamic and inhumane". It said the toll was 12 dead policemen and a child.
Twelve people were wounded in the blast, nine of them policemen and three civilians, said Daoud Ahmadi, spokesman for the Helmand provincial governor.
It comes after a string of destabilizing assassinations of high-profile southern leaders, including President Hamid Karzai's younger brother, and just days after suicide attackers with guns killed 19 people, most of them children.
(Read: "Ahmad Wali Karzai: A critical power broker")
Afghan forces took over security responsibilities in Lashkar Gah this month, the most contentious of the first seven areas for which foreign troops handed over duties.
The gradual transition of security control to Afghan forces is due to be completed by the end of 2014.
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