|Police have repeatedly been the target of attacks in Lashkar Gah, a city in Helmand province [EPA]
A suicide bomber has rammed a car packed with explosives into a police truck outside a bakery in southern Afghanistan, killing at least two civilians, officials have said.
The attacker had apparently been waiting in the car near the gates of the police headquarters in Lashkar Gah, the main city in Helmand province, on Tuesday morning, said provincial Police Chief Kamaluddin Sherzai.
Two civilians were killed in the blast, one man and one young boy, said provincial government spokesperson Daoud Ahmadi.
Another 26 people were wounded, including 10 police officers and six children, he said.
Taliban spokesperson Qari Yousef Ahmadi claimed responsibility for the attack, which came hours after the group released a formal statement rejecting claims that it has become splintered or that it or any of its allies have ties to the Pakistani government.
The Taliban said its campaign was "at its strongest and unified more than it has been at any other stage", and denied that it had bases in Pakistan.
The US and other countries claim that the Taliban retains numerous safe havens and bases in Pakistan's tribal areas, which it uses to stage attacks into neighbouring Afghanistan.
In the statement on Tuesday, the Taliban also rejected US charges that the Haqqani network, a key affiliate, had ties to Pakistan's intelligence service.
The announcement could be an attempt to give the Pakistani government some breathing room as Islamabad comes under increasing pressure to take action against fighters operating within its borders.
In the wake of three major attacks in the Afghan capital in the past two weeks, US officials have ramped up their public comments alleging the Pakistani government backs the Haqqani network, which is believed to be behind a number of attacks in and around Kabul.
The Afghan government, meanwhile, has increased its protests against cross-border artillery attacks it blames on Pakistan.
In a statement released on Monday, the Afghan government said that Afghan-Pakistan relations will suffer if the attacks in eastern Afghanistan continue.
A NATO forces spokesperson said on Monday that the Haqqani network is still operating out of Pakistan.
"We have no credible intelligence indicating that the Haqqani network has eliminated their operating safe havens in Pakistan," said Brigadier General Carsten Jacobson, speaking for NATO forces in Afghanistan.
"They continue to plan and execute operations from across the border."