The government of Pakistan said its air force shot down two Indian aircraft inside Pakistani airspace on Wednesday after the Indian Air Force crossed the line of control - the de facto border between the two countries in disputed Kashmir.

The alleged incident comes a day after Indian jets launched airstrikes in Pakistan territory in the first such incursion since the 1970s, and if confirmed, would mark a major escalation of hostilities between the two nuclear-armed neighbors.

Maj. Gen. Asif Ghafoor, spokesperson for the Pakistan armed forces, said in a tweet Wednesday that one Indian aircraft fell inside Pakistan-administered Kashmir, while another fell within the Indian-administered region of Kashmir. One pilot had been arrested, he said.

A post from the official Twitter account of the Pakistan government confirmed that its air force had shot down the two planes, following strikes conducted by Pakistan.

There has not been official comment from the Indian Air Force or government, and CNN could not independently verify Pakistan’s claims.

Meanwhile, a statement from the Pakistan Foreign Ministry said that Islamabad carried out aerial strikes on “nonmilitary targets” across the line of control (LoC) from within Pakistani airspace, while accusing India of “carrying out acts of terror in Pakistan.”

Pakistan said its strike was “not a retaliation” to the Indian operation and stressed that “Pakistan has therefore, taken strikes at nonmilitary target, avoiding human loss and collateral damage.”

Sole purpose being to demonstrate our right, will and capability for self defense. We have no intention of escalation, but are fully prepared to do so if forced into that paradigm. That is why we undertook the action with clear warning and in broad daylight,” the statement said.

Pakistan Prime Minister Imran Khan had previously promised retaliation “at the time and place of Pakistan’s choosing” and directed the country’s armed forces to remain prepared for all eventualities in response to the Indian strikes.

Flights to several Indian airports were suspended Wednesday, according to multiple Indian airlines on Twitter.

In separate tweets, Jet Airways, Vistara, Indigo and GoAir airlines announced the suspension of flights to airports at Amritsar, Chandigarh, Srinagar, Jammu & Leh.

‘Further escalation’

Earlier on Wednesday, Indian Foreign Affairs Minister Sushma Swaraj said the country does not want “further escalation” with Pakistan.

Speaking at a foreign ministers meeting between Russia, India, and China in Wuzhen, China, on Wednesday, Swaraj said Tuesday’s strike was “not a military operation” but “a preemptive strike against the terrorist infrastructure of Jaish-e-Mohammed.”

India blames the militant group Jaish-e-Mohammed (JeM) for a suicide car bomb attack in Indian-administered Kashmir, which killed 40 Indian paramilitary soldiers on February 14.

India had previously said that Pakistan had a “direct hand” in the attack – the deadliest on security forces since the beginning of the insurgency in the late 1980s. Pakistan has vehemently denied having a role in the incident.

Swaraj said that Tuesday’s pre-dawn operation was launched because of the “continuing refusal of Pakistan to acknowledge and act against terror groups on its territory.” The military action was based on “credible information” that militants were planning other attacks in various parts of the country, Swaraj said.

In its Foreign Ministry statement Wednesday, Pakistan said that “India has been trying to establish what they call ‘a new normal’ a thinly veiled term for doing acts of aggression at whatever pretext they wish on a given day. If India is striking at so called terrorist backers without a shred of evidence, we also retain reciprocal rights to retaliate against elements that enjoy Indian patronage while carrying out acts of terror in Pakistan.”

US Secretary of State Mike Pompeo spoke with his counterparts in India and Pakistan and urged both sides to “exercise restraint, and avoid escalation at any cost.”

“I also encouraged both ministers to prioritize direct communication and avoid further military activity,” he said Wednesday, in the first statement by the US government over the incident.

Reaction amid escalating tensions

Tensions between the two sides have escalated sharply since India’s airstrike on Tuesday. At an election rally a few hours after Tuesday’s airstrikes, Indian Prime Minister Narendra Modi did not refer to the attack directly, but spoke about protecting India. “I want to assure my countrymen that the country is in safe hands,” he said.

President of Modi’s ruling Bharatiya Janata Party (BJP) Amit Shah praised the “bravery and valor of our armed forces,” in a Twitter post.

“Today’s strong action shows the will and resolve of a New India. Our New India will not spare any acts of terror and their perpetrators and patrons,” he tweeted.

The Indian government had been weighing up how to respond to February’s attack in Indian-administered Kashmir, conducting raids over the past two weeks to weed out militants hiding in the region.

Skirmishes along the LoC have escalated since the Indian airstrikes. On Tuesday, Pakistan troops opened fire at 15 places across the LoC in Jammu and Kashmir, injuring five Indian soldiers, army spokesperson Devender Anand told CNN.

Harsh V Pant, a professor in international relations at King’s College London, told CNN that for the past few decades the Indian government had chosen not to retaliate after terror attacks in Kashmir.

But India is now at a point where it is choosing to escalate the situation, adding that India’s military action follows public anger over the attack.

China, which shares a border with both countries, called on Pakistan and India to “exercise restraint” after news of the airstrikes broke.

“Both India and Pakistan are important countries in South Asia,” Chinese Foreign Ministry spokesperson Lu Kang said during a daily press briefing Tuesday. “We hope that both sides can exercise restraint, and take actions that can contribute to the region’s stability and improve their mutual relationship, but not the opposite.”

Tumultuous history

Kashmir, a largely mountainous region located between India and Pakistan, has had a tumultuous history. The region has been bitterly contested by both India and Pakistan following the partition of the two countries in 1947, leading to three wars and numerous other skirmishes.

The February attack came more than two years after armed militants entered an Indian army base in the garrison town of Uri, about 63 miles (102 kilometers) from Srinagar – killing 18. India later said it had used ground troops to strike terrorist targets across the LoC in response to the Uri attack, something which Pakistan denied.

Days after February’s attack four Indian army personnel were killed in a gunfight with militants in the Pulwama district of Indian-administered Kashmir.

Separatist violence in the region has killed more than 47,000 people since 1989, although this toll doesn’t include people who have disappeared due to the conflict. Some human rights groups and nongovernmental organizations put the death toll at twice that amount.