In March 2014, the US military paid an Afghan man just over $1,000 to compensate for killing his civilian son in an operation near the border with Iran, according to US military records released to Reuters.

Six months later, another Afghan father was given $10,000 by the US military after his child, also a civilian, was killed in an American-led military operation in the same province.

And 68-year-old Haji Allah Dad lost 20 relatives, including his brother and sister-in-law, in a US and Afghan special forces operation near the northern city of Kunduz last November.

Allah Dad said he received no money from the US military, though he did get compensation from the Afghan government.

Nearly 16 years since invading Afghanistan, the United States has no standardised process for making compensation payments to the families of thousands of Afghan civilians killed or injured in US-led military operations.

It first started paying the families of Afghan victims as a way to counter Taliban militants who were doing the same.

America's approach to compensation is arbitrary by design as it tries to negotiate Afghanistan's cultural and regional sensitivities as a foreign military force.

But civil activists say the system is unfair and confusing for often poor and uneducated Afghans.

A Pentagon spokesman said the military leaves the decision on how much to pay to commanders on the ground because they are best positioned to judge the incidents.

"Condolence payments in Afghanistan are based on cultural norms of the local area, advice from Afghan partners, and the circumstances of the event," said spokesman Adam Stump.

"US commanders in theater are therefore empowered to make decisions regarding payments as they have the greatest understanding of these factors," Stump said.

It is unclear how the US military puts these factors in monetary terms.

Washington started making condolence payments in Afghanistan in 2005 after realising that the Taliban was gaining influence and goodwill by giving civilians money after fatal US strikes, according to the Center for Civilians in Conflict, a US-based advocacy and research group.

The United States does not have to pay compensation to civilians killed in its military actions under international and national law.

However, it has made such payments going back to the Korean War in the 1950s. In some cases, it paid compensation to the relatives of civilians it killed in the Iraq conflict.

Critics warn the lack of standardisation in compensation payments means Afghan civilian victims are not treated equally as the conflict there grinds on.

The top US commander in Afghanistan has said several thousand more troops would be needed to break a stalemate with the Taliban.

"It's of great concern that we're talking about stepping up the way that we carry operations without a standard operating procedure for making condolence payments," said Marla Keenan, senior director of programs at the Center for Civilians in Conflict.

"A man in Kandahar may get $4,000 for his damaged car while a woman in Gardez gets $1,000 for her dead child. Civilians deserve better,” Keenan said.