The Pentagon has failed to disclose thousands of potentially lethal airstrikes by the US in Iraq, Syria, and Afghanistan over the course of several years, an investigation has found.

The Military Times reports that public summaries of operations in Iraq and Syria, current as of the end of January, exclude nearly 6,000 strikes dating to 2014 when Obama gave the go-ahead for action against ISIS.

It also discovered that in 2016 alone at least 456 US airstrikes on militants, conducted by drones and helicopters, in Afghanistan were not documented in a US Air Force database.

In 2016 alone at least 456 US airstrikes on militants, conducted by drones and helicopters, in Afghanistan were not documented

The Pentagon recorded 615 coalition airstrikes in Afghanistan meaning the revised number should be 1,071.

The US Central Command says the army and coalition members have conducted 13,989 strikes in Iraq and Syria (7,458 in Iraq, 6,531 in Syria) from the end of 2016 to January 31 2017.

The unreported airstrikes opens up the very real possibility that scores more civilians and militants died at the hands of the US military, than previously reported.

The incomplete data could go back to October 2001, the year the war on terror started, according to the Military Times.

The news source also says the unreported figures casts into doubt the truth of war statistics disclosed by the Pentagon and the expense of the military action taken in the Middle East.

The Military Times reported: 'Most alarming is the prospect this data has been incomplete since the war on terrorism began in October 2001.

'If that is the case, it would fundamentally undermine confidence in much of what the Pentagon has disclosed about its prosecution of these wars, prompt critics to call into question whether the military sought to mislead the American public, and cast doubt on the competency with which other vital data collection is being performed and publicized.'

Airstrikes from AH-64 Apache attack helicopters are unreported by US Central Command's (CENTCOM) data collection

The extra airstrikes were not reported in a US Air Force open-source database that is 'relied on by Congress, American allies, military analysts, academic researchers, the media and independent watchdog groups.'

An army official, who wished to remain anonymous, said that the US is not trying to cover up the number of airstrikes it conducts, saying the military doesn't record bombings from certain aircraft such as from AH-64 Apache attack helicopters.

He said: 'It is really weird. We don't track the number of strikes from Apaches, for example.

'I can tell you, unequivocally, we are not trying to hide the number of strikes. That is just the way it has been tracked in the past. That's what it's always been.'

Despite the official's claims, an Air Force official told Military Times in December that its monthly airpower summary of activity in Iraq and Syria specifically represents the entire US-led coalition 'as a whole, which is all 20 nations and the US branches.'

The Air Force's open-source database says it includes all such missions as part of its airstrike totals.

The media and others have depended on these figures for years believing they are a comprehensive tally of all American and coalition activity.

However no one from the military ever has come forward to clarify that the statistics are incomplete.

The Pentagon and Army did not immediately respond to requests for comment.