Two US lawmakers have urged Secretary of Defense Lloyd Austin to overhaul how the military tracks civilian casualties, arguing that the Pentagon is undercounting the number of noncombatants killed in war zones.

Iran Press/America: "The Department reported 23 civilians killed and 10 civilians injured as a result of US military operations last year, but estimates from credible civilian casualty monitors and the United Nations suggest that number is almost five times higher," Senator Elizabeth Warren and Congressman Ro Khanna wrote in a letter on 30 June that was released on Tuesday.

"As a first step... we request that you review why these significant discrepancies in civilian casualty counts persist, and take steps to ensure that US military investigations into civilian casualties give greater weight to external sources of information rather than relying solely on its own internal records and sources when assessing third party reports of civilian harm."

The US military reported last month that it was responsible for unintentionally killing 23 civilians in foreign war zones in 2020, far below figures compiled by non-governmental agencies. But it also acknowledged more civilian deaths from previous years.

The tally included civilian fatalities from operations in Iraq, Afghanistan, Somalia, Yemen, and Nigeria, according to a Pentagon report.

Most of the civilian casualties were in Afghanistan, where the Pentagon said it was responsible for 20 deaths, according to the public section of the report.

The US Department of Defense "assesses that there were approximately 23 civilians killed and approximately 10 civilians injured during 2020 as a result of US military operations", the document read, part of an annual report required by Congress since 2018 - although parts of it remain secret.

One civilian was killed in Somalia in February 2020 and another in Iraq in March. The document released to the public does not specify when or where the 23rd victim was killed.

The document also said that, although Congress allocated $3m to the Pentagon in 2020 for financial compensation to the families of civilian victims, no such compensation had been paid.

In the letter, the lawmakers criticised the Department of Defense for not using any of the $3m for condolence or "ex gratia" payments, which they say would have been more than enough for payments to every victim's family.

"This is unacceptable and not how we uphold our nation's values and advance our interests overseas. We urge you to take a more serious look at both of these issues," the letter reads.

"We need to openly consider all the costs, benefits, and consequences of military action, and that includes doing everything we can to prevent and respond to civilian harm. 

"Strengthening investigations, accurately and transparently reporting on civilian harm, expressing condolences for harm when it happens, and learning from these incidents to prevent harm in the future are all essential steps that reinforce the importance of protecting civilians as a national security priority and as a moral and ethical imperative."

Non-governmental organisations (NGOs) frequently publish much higher civilian death tolls in areas where the US military is active around the world.

Airwars, an NGO which lists civilian victims of air attacks, said that their most conservative estimates show 102 civilians killed in US operations around the world in 2020 - five times higher than the official Pentagon figures.

The United Nations Assistance Mission in Afghanistan (UNAMA) counted 89 dead and 31 wounded in operations by US-led coalition forces during the same period, Airwars said.

In Somalia, where the Pentagon recognises only one civilian death, Airwars and other NGOs estimate the death toll at seven, while in Syria and Iraq local sources report six dead, the NGO said.