"Pakistan will definitely respond to Indian aggression", Foreign Minister Shah Mehmood Qureshi categorically announced while addressing media on Tuesday.
He claimed the Indian jets were forced to return "owing to the timely response of the Pakistan Air Force".
The escalation comes in the wake of a suicide bombing that killed dozens of troops in Indian Kashmir and sent tensions soaring.
New Delhi had threatened to retaliate after the deadliest attack in three decades in Kashmir killed more than 40 Indian paramilitaries.
The Indian news agency ANI, citing unnamed military sources, said that 12 Mirage 2000 fighter jets had attacked a "terrorist camp". "I pledge on this soil, I will not let the country die, I will not let the country stop".
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Hours after India undertook a non-military preemptive strike in Balakot, foreign nations have urged India and Pakistan to maintain good relations for peace in South Asia.
British officials have been in "close contact" at senior levels in New Delhi and Islamabad, besides taking steps to promote worldwide efforts to avoid escalation. He said there were no casualties and no damage.
On the intervening night of 25 and 26 February, the Indian Air Force carried out air strikes across the LoC at around 3:30 am. Pakistan has denied involvement in the attack but has vowed to respond to any Indian military operation against it.
The unspecified number of Indian aircraft tried to intrude from three points before crossing the LoC from the Muzaffarabad sector, he said. There was no immediate explanation for the differing accounts, but India and Pakistan routinely contradict one another.
Pakistani officials confirmed that Indian Air Force jets crossed into the country's territory, but in a series of tweets, military spokesman Maj. Pakistan, however, said the aircraft had "released a payload" while escaping from the jets scrambled to intercept it, and claimed it caused no casualties. Kashmiri resistance groups in Jammu and Kashmir have been fighting against Indian rule for independence, or for unification with neighboring Pakistan.
India accuses Pakistan of sheltering and supporting groups like Jaish-e-Muhammad.
India said its warplanes attacked a militant camp where Pakistan-backed fighters were preparing suicide attacks on its cities, killing a "very large number" of militants from the Jaish-e-Mohammad (JeM) group.