Eyewitnesses said the powerful bombing left a huge crater outside the police training centre.
At least three Afghan policemen were killed when a suicide bomber detonated an explosive-laden car at a training centre in the southern province of Helmand on Saturday, officials said.
The attack in Nad Ali district, which also wounded nine people, was claimed by the Taliban and comes in the midst of the militant group's annual spring offensive launched last month, in what is expected to be the worst fighting season in 15 years of war.
"Three policemen were killed in a suicide car bombing in Nad Ali," Helmand police chief Abdul Rahman Sarjang told Agence Frace Presse.
"Seven police and two civilians were among the wounded," he added.
Eyewitnesses said the powerful bombing left a huge crater outside the training centre.
The attack comes after a period of relative calm in Helmand, a Taliban hotbed, for more than a month when many militants left the frontlines to assist in harvesting poppies for opium - the group's main source of revenue.
Taliban spokesman Qari Yousuf Ahmadi said the militants were behind the bombing but claimed that dozens of policemen were killed in the attack.
The insurgents have frequently used roadside bombs, ambushes and suicide assaults during nearly 15 years of war against the government and NATO forces.
The Taliban have vowed "large-scale attacks" across Afghanistan in this year's spring offensive - dubbed Operation Omari in honour of its late founder Mullah Omar, whose death was announced last year.
The attack on Saturday came just as the Afghan government is expected to finalise a peace deal with another militant insurgent group within days, an official and a representative of the group said.
The deal is partially symbolic as the group in question, Hezb-i-Islami, has been essentially inactive for years. However, it provides a much-needed success for the beleaguered administration of President Ashraf Ghani and potential template for ending Kabul's 15-year war with the still active and far more dangerous Taliban.
Under the terms of the 25-point agreement, a draft of which has been seen by The Associated Press, the group would end its war against Kabul, commit to respecting the Afghan constitution, and cease all contact with other armed, anti-government groups. In return its members would receive amnesty and its prisoners in Afghan jails would be released.
Ataul Rahman Saleem, deputy head of Kabul's High Peace Council, told AP that the deal with the armed wing of Hezb-i-Islami could be completed on Sunday, after two years of negotiations. A senior representative of Hezb-i-Islami, Amin Karim, also said he expected President Ashraf Ghani to approve the final version of the agreement on Sunday.
Hezb-i-Islami is led by warlord and former prime minister Gulbuddin Hekmatyar, who is accused of killing thousands of people in Kabul during the 1992-1996 civil war. His location is unknown but he could soon return to Kabul to sign a formal peace deal and take up residence.