New Delhi, India(CNN) Pakistan has promised retaliation "at the time and place of its choosing" after India conducted airstrikes on an alleged terrorist training camp inside Pakistan territory, in a significant escalation of hostilities between the nuclear armed powers.
Pakistan's Prime Minister, Imran Khan, directed the country's armed forces to remain prepared for all eventualities in response to the strikes, the first such incursion by Indian Air Force planes across the border between the two countries since the India-Pakistan war of 1971.
"India has committed uncalled for aggression to which Pakistan shall respond at the time and place of its choosing," Khan's office said in a statement on Tuesday.
Earlier on Tuesday, Indian Foreign Secretary Vijay Gokhale told reporters in New Delhi that "a very large number" of militants were "eliminated" in the operation, which he said came in response to "credible intelligence" about potential terrorist attacks.
Pakistan disputed India's claim that it targeted a terrorist camp and denied that numerous militants had been killed, calling it "a self serving, reckless and fictitious claim" by the Indian government.
"This action has been done for domestic consumption being in election environment, putting regional peace and stability at grave risk," Khan's office said.
The two sides have differing versions of what occurred on Tuesday.
Pakistan said Indian jets made two attempts to cross the border into Pakistani territory but were driven back. They were successful on their third attempt and dropped their "payload" near the town of Balakot in Pakistan's northern Khyber Pakhtunkhwa Province, according to Pakistan Maj. Gen. Asif Ghafoor.
Balakot is a town several miles from the border of Pakistan-administered Kashmir. It lies about 100 miles from the Pakistan capital Islamabad and about 40 miles from Abbottabad, the town where US Special Forces killed Osama bin Laden on May 2, 2011.
Ghafoor alleged that Indian jets crossed the LoC and were pushed back by Pakistan Air Force jets that were "scrambled" to the scene.
"Indian (aircraft) intruded from Muzafarabad sector. Facing timely and effective response from Pakistan Air Force released payload in haste while escaping which fell near Balakot," said Ghafoor, in a statement posted on his official Twitter account.
Indian authorities confirmed Tuesday its aircraft had crossed the line of control to carry out airstrikes, but did not give details on where their planes went or where munitions landed.
Foreign Secretary Gokhale said India targeted a militant training camp run by Jaish-e-Mohammed, the group India blames for a suicide car bomb attack in Pulwama in Indian administered Kashmir that killed 40 Indian paramilitary soldiers on February 14.
India said the alleged camp was a military training facility headed by Maulana Yousuf Azhar, the brother-in-law of Masood Azhar -- the chief of Jaish-e-Mohammed.
Tensions between the two sides have escalated sharply since the Pulwama bombing, which comes ahead of India's national elections scheduled to be held by May.
At an election rally a few hours after the 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 valour 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.
India has claimed Pakistan had a "direct hand" in the bombing and promised retaliation, including commercial and diplomatic steps to "isolate" Pakistan internationally.
Pakistan has vehemently denied having a role in the incident.
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."
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.