Many of the green-on-blue attacks on NATO forces serving in Afghanistan could be the direct handiworks of Taliban insurgents, according to a U.S. marine general supervising the operations of coalition troops in the war-torn country.

U.S. Marine General John Allen, overall chief of NATO deployment in Afghanistan, said on Thursday that up to 25 per cent of the insider attacks against foreign soldiers deployed in the country can be traced to the Taliban.

"Our view is it's about 25 per cent," Gen Allen was reported by Reuters as saying.

He clarified that the figures represent 'infiltrations' that were solely designed by the insurgent group as other 'killings' could have been motivated by other motives such as personal issues or mimic attacks that were intended to convince NATO that Taliban's hands were deep into Afghan's security forces.

Gen Allen's statement ran in counter with the official figures on insider attacks provided by the U.S. military leadership, which last week has indicated that 11 per cent of the green-on-blue assaults on foreign troops in Afghanistan could be blamed to the Talibans.

Yet NATO, according to Reuters, later explained in a statement that Gen Allen was not actually contradicting Pentagon's official numbers as his assessment mostly covered of attacks that occurred in the past years.

The lower figures pointed out by Pentagon were for the attacks that have been registered so far in 2012, NATO said.

According to Agence France Presse (AFP), 40 coalition troops have died so far in the current year due to attacks perpetrated by rogue elements of the Afghan security forces, including the similar incidents in the past two weeks that led to the deaths of 10 American service members.

Also, at least four Aussie Diggers have died in 2011 when Afghan security officers they were mentoring or working with turned their guns against then, The Australian reported.

Such occurrences, observers said, undermine efforts by NATO to accelerate the transition of security responsibility in the country from foreign troops to local security forces while at the same time create a wedge of distrust between NATO forces and their Afghan counterparts.

The numbers of such attacks have been noticeably climbing as NATO prepares to turnover more military duties to the Afghan government in light of its planned withdrawal from the Central Asian nation following more than a decade of conflict.

Other countries, which include Australia, France, New Zealand and the United Kingdom, plan to pull out their troops much earlier than the late 2014 complete drawdown earlier set by the United States.

Reuters said Gen Allen was briefed by Afghan President Hamid Karzai on the likelihood that foreign infiltrators, possibly from neighbouring Iran and Pakistan, could be directly involved in plotting such attacks.

It was reportedly suggested that a deeper look by NATO leadership on the matter could likely stem similar incidents in the future.

Gen Allen said whatever information that would be shared by Mr Karzai would be seriously studied by NATO.

"I'm looking forward to Afghanistan providing us with the intelligence that permits them to come to that conclusion," the NATO chief told Reuters on Thursday.

Meanwhile, U.S. Joint Chiefs of Staff chair General Martin Dempsey said earlier this week that his talks with Mr Karzai and other Afghan leaders led him to believe that the matter was also of prime concerns for Kabul.

""For the first time, I found that my Afghan counterparts are as concerned about the insider attacks as we are," Gen Dempsey was reported by AFP as saying.

Previous sentiments in Washington were like "it's been us pushing on them to make sure that they do more," the top U.S. general admitted.