KABUL, Afghanistan - A station wagon packed with Afghan civilians struck a roadside bomb in western Afghanistan, triggering an explosion that killed 16 people, 11 of them children, Afghan officials said.

The vehicle was travelling in Herat province's Shindand district when it hit the bomb, said Mohammad Salim, the police garrison chief for the district. Another four people in the car were wounded, he said.

Those in the car were part of the same extended family, Salim said. He did not provide further details. Provincial spokesman Muhiuddin Noori confirmed the casualty figures.

Civilians have been the overwhelming victims of the rise in violence in Afghanistan this year. Though civilian deaths attributed to NATO forces have decreased, a rise in roadside bombs and insurgent attacks means that more civilians are being killed.

Meanwhile, more details emerged about this week's killing of an American CIA employee in Kabul. A U.S. Embassy spokesman said that the dead worker was a facility maintenance employee.

"He provided essential support for the maintenance of the U.S. annex in Kabul," Gavin Sundwall said. "He was described to me as a valued member of the team and he will be sorely missed." U.S. officials have not named the complex as a CIA office, but former intelligence officials have confirmed that it was used by the CIA.

The American was shot dead Sunday evening by an Afghan worker at the building. Sundwall said previous reports that the Afghan worker was not authorized to carry a weapon inside the complex were premature, and that it was unclear whether that was the case.

A U.S. official in Washington said the Afghan attacker was providing security to the CIA office and that the American who died was working as a contractor for the CIA. The official requested anonymity because he was speaking about intelligence matters.

In the south on Tuesday, a suicide bomber rammed an explosives-packed vehicle into a police truck, killing two civilians.

The attacker in the southern city of Lashkar Gah, the main city in Helmand province, apparently was waiting in the car at the gates of the police headquarters just outside a bakery where officers regularly buy bread in the morning, said the deputy provincial police chief, Kamaluddin Sherzai. The bomber then slammed into a police truck that was parked at the shop, triggering the bomb, he said.

Two civilians -- one man and one young boy -- were killed in the blast, said provincial government spokesman Daoud Ahmadi. Another 26 people were wounded, including 10 police officers and six children, he said.

Taliban spokesman Qari Yousef Ahmadi claimed responsibility for the Lashkar Gah attack.

Hours earlier, the Taliban released a formal statement rejecting claims that the insurgency has become splintered or that the group or any of their allies have ties to the Pakistani government.

The statement said the Taliban insurgency "is at its strongest and unified more than it has been at any other stage," and denied that the movement has bases in Pakistan.

The claim runs contrary to U.S. and international assertions that the Taliban retain numerous safe havens and bases in Pakistan's tribal areas, used to stage attacks into neighbouring Afghanistan.

The Taliban also reject U.S. charges that the Haqqani network, a key affiliate, has ties to Pakistan's intelligence service. The group says Haqqani network founder Jalaluddin Haqqani is a key member of the Taliban leadership.

The Taliban statement appeared to be an attempt to give the Pakistani government some breathing room as Islamabad comes under increasing pressure to take action against insurgents within its borders.

In the wake of three major attacks in the Afghan capital in the past two weeks, U.S. 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 upped its protests against cross-border artillery attacks it blames on Pakistan.

On Monday, the Afghan government said that Afghan-Pakistani relations will suffer if the attacks in eastern Afghanistan continue.

A NATO forces spokesman in Afghanistan said Monday that the Haqqani network is still very much operating out of Pakistan.

"We have no credible intelligence indicating that the Haqqani network has eliminated their operating safe havens in Pakistan," said Brig. Gen. Carsten Jacobson. "They continue to plan and execute operations from across the border."

In Kabul, meanwhile, tensions between different political factions were on the rise as hundreds of demonstrators, led by former intelligence chief Amrullah Saleh, accused the government of mishandling the investigation into last week's killing of former President Burhanuddin Rabbani.

Saleh called on international officials to investigate the assassination, saying he did not trust the Afghan government to do the work honestly.