Russian Foreign minister Sergey Lavrov on Tuesday said United States should provide an explanation to alleged claims of unmarked helicopters delivering weapons to terrorists groups, including Islamic State (ISIS) in northern Afghanistan.

After meeting his Pakistani counterpart, Khwaja Muhammad Asif, Lavrov, in a press conference in Moscow, dredged up past claims regarding U.S. and NATO's alleged involvement in supplying weapons to ISIS in unmarked helicopters.

He said, “We still expecting from our American colleagues an answer to the repeatedly raised questions, questions that arose on the basis of public statements made by the leaders of some Afghan provinces, that unidentified helicopters, most likely helicopters to which NATO [North Atlantic Treaty Organization] in one way or another is related, fly to the areas where the insurgents are based, and no one has been able to explain the reasons for these flights yet. …. In general they [the United States] try to avoid answers to these legitimate questions.”

Lavrov revived the conspiracy theory that first reared its head in May 2017 when the governor of Afghanistan’s northern Sar-e Pol province Mohammad Zahir Wahdat alleged unmarked military helicopters landed in a known military stronghold.

However, to explain the lack of substantiate proof to support the claims, he said none of the security forces in the area were able to film the incident, Drive reported. He did not provide any reason as to why they were unable to do so.

The claims made by the governor didn’t point at any particular country, but Russian Ministry of Foreign Affairs released a statement, based on news reports, which claimed the helicopters had flown to the main international airport in the city of Mazar-e-Sharif, which also hosts a major base belonging to the NATO-led coalition in Afghanistan.

Later, many media outlets in Russia jumped on the bandwagon, citing un-named locals who claimed they witnessed a number of these unmarked helicopters delivering weapons to the local terror groups in the region.

In June, referring to the reports on the helicopters, Russia Foreign Ministry spokesperson Maria Zakharova told reporters U.S. should provide a rational explanation behind the unmarked helicopters carting weapons to terrorists groups.

“We’ve taken note of new reports about unmarked helicopters ferrying the fighters of ISIS Afghan branch, as well as weapons and munitions for them, in eastern Afghanistan,” Russia Foreign Ministry spokesperson Maria Zakharova told reporters during a press briefing Wednesday.

“It is symptomatic that neither the Afghan authorities nor the U.S. and NATO military contingent officials in Afghanistan have offered a rational explanation for the increased number of flights made by unidentified helicopters providing support to ISIS fighters in many Afghan provinces,” Zakharova stated. “Silence in this case is becoming increasingly conspicuous.”

Although there is no basis to add credibility to this theory, the allegations cannot be completely written off as an elaborate ruse by Russia to encapsulate U.S. in a conspiracy, as the country has a history of arming terrorists in the past.

A Conflict Armament Research report published in December 2017 stated U.S. and Saudi Arabia were responsible for supplying weapons to ISIS.

“The United States and Saudi Arabia supplied most of this materiel without authorization, apparently to Syrian opposition forces. This diverted materiel, recovered from IS forces, comprises exclusively Warsaw Pact–caliber weapons and ammunition, purchased by the United States and Saudi Arabia from European Union (EU) member states in Eastern Europe,” the report found.