KABUL — The US-led NATO mission in Afghanistan may be exaggerating successes of raids designed to kill or capture insurgent leaders, a flagship strategy in the 10-year war, a report warned Thursday.

The International Security Assistance Force (ISAF) hails the raids as one of the most effective tactics against the insurgency, but the Afghanistan Analysts Network (AAN) says data from December 2009 to September 2011 is inconsistent.

"The lack of transparency is particularly apparent in the case of the insurgent ?leaders? that were reportedly being killed and captured; there is no way to properly evaluate these claims," said the AAN report on its website.

But ISAF slammed the report as "disingenuous" for making false comparisons of data that "inevitably lead to faulty conclusions on mission progress".

Two days ago, the military said the number of Taliban attacks had declined for the first time and that the Taliban has failed in recent months to seize back territory lost in US-led offensives in the south.

Basing its data on 3,771 press releases announcing the deaths of at least 3,873 people and the detentions of another 7,146, AAN said ISAF often interchanges the terms "facilitator" and "leader" without explaining why.

It also said statistics in press releases did not tally with more grandiose figures released separately by ISAF to media outlets.

Although it was unclear to what extent this was intentional, "it should make policy-makers and analysts evaluating ISAF?s progress think twice about accepting these body-count figures without more serious scrutiny," AAN said.

On September 3, an ISAF release said security forces had captured or killed more than 40 Al-Qaeda insurgents in eastern Afghanistan this year.

But a tally of previous releases add up to 22 killed and 10 captured, many of which, AAN points out, are simply noted as having had "suspected ties".

AAN concedes that the press releases themselves do not represent a complete figure, given that there may have been unreported operations, and more deaths and detentions per incident than counted.

But ISAF said it was wrong to compare figures from its press releases with broader statistics as regular updates are "not" an authoritative database of all ISAF operations, "or even a representative sample from them".

"Hence any analysis based on them which draws broader conclusions on ISAF operations overall is flawed," said spokesman Lieutenant Colonel Jimmie Cummings.

ISAF also defended its terminology, saying that leaders in charge of other insurgents can also be classified as facilitators who assist operations "much in the same manner as the authors of this report label themselves as researchers, writers, commentators and editors".

Last month, ISAF also disputed UN statistics showing a 39 percent increase in violence in the war-torn country.

NATO allies, under pressure from voters in the West increasingly fed up with the long and costly war, are scheduled to withdraw combat troops from Afghanistan by the end of 2014.