It said a newly obtained trove of confidential documents covering more than 1,300 reports of civilian casualties undercuts the government's portrayal of a war fought with precision bombs.

Pledges of transparency and accountability, it said, had regularly fallen short.

"Not a single record provided includes a finding of wrongdoing or disciplinary action," the paper reported in what it said was the first of a two-part series.

While several of the cases mentioned by the Times have been previously reported, it said its investigation showed that the number of civilian deaths had been "drastically undercounted."

Among three cases cited was a July 19, 2016 bombing by US special forces of what were believed to be three Islamic State group staging areas in northern Syria. Initial reports were of 85 fighters killed. Instead, the dead were 120 farmers and other villagers.

Another example was a November 2015 attack in Ramadi, Iraq after a man was seen dragging "an unknown heavy object" into an IS position. The "object," a review found, was a child, who died in the strike.

Poor or inadequate surveillance footage often contributed to deadly targeting failures, the report said.

More recently, the United States had to retract its claim that a vehicle destroyed by a drone on a Kabul street in August had contained bombs. Victims of the strike, it turned out, were 10 members of a family.

Many civilian survivors of US attacks, the report says, were left with disabilities requiring expensive treatment, but condolence payments numbered fewer than a dozen.

Asked for comment, Captain Bill Urban, spokesman for the US Central Command, told the Times that "even with the best technology in the world, mistakes do happen, whether based on incomplete information or misinterpretation of the information available. And we try to learn from those mistakes.

"We work diligently to avoid such harm. We investigate each credible instance. And we regret each loss of innocent life."

The US air campaign in the Middle East grew rapidly in the final years of former president Barack Obama's administration, as public support waned for the seemingly endless ground wars.

Obama said the new approach using aircraft controlled from far away represented "the most precise air campaign in history," able to keep civilian deaths to a minimum.

But over a five-year period, US forces executed more than 50,000 airstrikes in Afghanistan, Iraq and Syria, the report said.

In compiling its report, the Times said its reporters had "visited more than 100 casualty sites and interviewed scores of surviving residents and current and former American officials."