Pakistani F-16 fighter jets fly past during a Pakistan Day military parade in Islamabad on March 23, 2017.
CNN  — 

The US is looking into reports that Pakistan misused American-made F-16 jets during an aerial engagement with India last week that brought the two nuclear armed neighbors to the brink of conflict.

Both India and Pakistan launched airstrikes over the Line of Control – the de facto border that separates the two countries in disputed Kashmir – in the first such incursion since 1971. An Indian jet was shot down in the dogfight and its pilot held in Pakistan custody for several days before Islamabad released him back to New Delhi on Friday.

The Indian Air Force said that Pakistan used US-made F-16 fighter jets in the raid that brought down the Indian pilot on Wednesday, in a possible violation of the terms of use by the US.

Pakistan has stated that no F-16s were used in the operation, though it hasn’t specified what military equipment was involved.

A US Department of State official told CNN that it was “aware of reports” that the use of F-16 jets may have been in violation of the terms of use agreement and is “looking into them.”

Speaking at the US Institute of Peace in Washington, DC on Monday, Pakistan’s ambassador to the US, Asad Majeed Khan, said that he was not aware of any request from the US about the alleged use of F-16s.

“On F-16, I don’t know, India has been alleging so many other things. We don’t get into every single one of them. I am not aware of request from the US side about the F-16,” he said.

Strong military relationship with US and China

Following the 9/11 attacks and subsequent US invasion of Afghanistan in 2001, Pakistan became a major US ally in the Bush administration’s so-called war on terror and a big recipient of American military aid.

Arms deals with Pakistan reached $3.5 billion in 2006, making the South Asian nation the US’s biggest arms purchaser. In its haul, Pakistan bought dozens of F-16 fighter jets as well as a variety of bombs and anti-ship missiles.

As part of the purchasing agreement, the US puts certain restrictions on how its military equipment can be used. It is unclear what restrictions were placed on the use of Pakistan’s F-16 jets.

The US began suspending military aid to Pakistan in 2016 over what it saw as a failure by the Pakistani government to adequately clamp down on terror groups within its borders. In 2018, it was estimated that the assistance being suspended was more than $1 billion.

Pakistan is also one of the largest buyers of Chinese weapons. Between 2008 and 2017, Islamabad purchased more than $6 billion of Chinese arms, according to think tank CSIS. And Prime Minister Imran Khan has been determined to keep the special relationship with Beijing strong. “We need to use China as an inspiration to lift our people out of poverty,” he has said.

Pakistan’s own fighter jets that it makes domestically are Chinese-designed JF-17s.

An uncertain narrative

On Thursday, Indian Air Force officials said that parts of an AMRAAM air-to-air missile that can only be used on F-16 jets had been recovered in Indian territory.

According to Air Vice Marshal RJK Kapoor, Pakistani jets attempted to target Indian “military installations” over the Line of Control but were “intercepted” by the Indian Air Force.

Pakistan denied targeting military posts but said it was forced to take action after India launched airstrikes on what India said was a terrorist training camp in the Balakot region of Pakistan. Pakistan also denied the existence of such a camp.

“We only wanted to tell India that we have the capability, if you come and carry out an activity on our land, we can also come over and do the same in your land,” Khan said last Wednesday.

During a phone call with Pakistan Prime Minister Imran Khan on Sunday, British Prime Minister Theresa May stressed the “importance of Pakistan taking action against all terrorist groups, in support of global efforts to combat terrorism.”

The stand-off has seen both sides engage in increased military exchanges across the heavily fortified Kashmir border. At least four Pakistani civilians have died and eight were injured in cross-border shelling from India since Thursday night in several areas in Pakistani-controlled Kashmir, Raja Moazzam, Pakistan state director for disaster management, told CNN Friday.

Moazzam said dozens of houses have been damaged from shelling and hundreds of people have been moved to other areas. About 600 people are taking shelter in state-run camps, he said.

India has accused Pakistan of initiating the exchange of fire.

The immediate trigger for the latest confrontation was a suicide car bomb attack on February 14 in Indian-controlled Kashmir, which killed 40 Indian paramilitary soldiers. India blamed the terrorist group Jaish-e-Mohammed for the attack, the deadliest on security forces since the beginning of the insurgency in the late 1980s.

With reporting from CNN’s Ryan Browne