Indian fighter jets have crossed the ‘line of control’ in Kashmir and attacked ‘terror camps’ in a rare ratcheting up of tensions with Pakistan.

India has carried out aerial bombing over the disputed ceasefire line in Kashmir for the first time since it went to war with Pakistan in 1971, and claims to have hit a large militant training camp.

The country’s foreign secretary, Vijay Gokhale, said in a briefing that Delhi had received credible intelligence that the militant group Jaish-e-Mohammed (JeM), which killed 40 Indian security personnel in a suicide bombing this month, was training fighters for similar attacks.

“In the face of imminent danger, a pre-emptive strike became absolutely necessary,” Gokhale said.The attack was celebrated in India, but it was unclear on Tuesday whether anything significant had been struck by the fighter jets, or whether the operation had been carefully calibrated to ease popular anger over the 14 February suicide bombing without drawing a major Pakistani reprisal.

Pakistan, which was the first to announce the incursion of Indian fighter jets early on Tuesday morning, said the war planes made it up to four miles inside its territory before they were rebuffed, dropping their payloads without casualties or damage.

Pakistan’s armed forces spokesman, Maj-Gen Asif Ghafoor, tweeted on Tuesday morning that the Indian jets had dropped their bombs in an empty forested area. “No infrastructure got hit, no casualties,” he wrote.

Imran Khan, the Pakistani prime minister, said India’s claim that it had hit a terrorist training camp was “a self-serving, reckless and fictitious claim”.

“This action has been done for domestic consumption in the election environment, putting regional peace and stability at grave risk,” Khan said, referring to India’s general election which starts in two months.

He said foreign and local journalists would be taken to the site of the alleged bombing “to see the facts on the ground”. The army had been advised “to prepare for all eventualities”, Khan added.

The attacks overnight followed nearly a fortnight of sabre-rattling between the nuclear-armed neighbours over the 14 February suicide bombing, in which India has claimed Pakistan had a “direct hand”. JeM is based in Pakistan but Islamabad has rejected any responsibility for the attack.

Gokhale said Indian jets struck JeM’s largest training camp in the Balakot area in the early hours of Tuesday. “A very large number of JeM terrorists, trainers, senior commanders and groups of jihadis being trained for fidayeen[suicide] action were eliminated,” he said.

“It changes the game significantly by raising the costs for Pakistan,” said Khalid Shah, a research fellow at the Delhi-based Observer Research Foundation.

He said the training facility, which he described as being in thick forest on a hilltop, was far away from any civilian settlements, and was overseen by the brother-in-law of the JeM chief, Masood Azhar.

Significantly, Balakot is in the province of Khyber Pakhtunkhwa, about 50 miles from the line of control and well into accepted Pakistan territory. An attack there would represent an escalation from previous Indian reprisals, analysts said.

“It changes the game significantly by raising the costs for Pakistan,” said Khalid Shah, a research fellow at the Delhi-based Observer Research Foundation.

Pakistan’s foreign minister, Shah Mahmood Qureshi, told a media briefing that Pakistan was planning its response. “This is an aggression against Pakistan and Pakistan will respond,” he said. 

Islamabad released pictures on social media showing uprooted trees and cratered soil, which it claimed was the extent of the damage from the Indian bombing.

The conflicting narratives over the attack echo the September 2016 “surgical strikes”, in which India claimed to have sent special forces to destroy militant facilities over the ceasefire border – an attack that Pakistan still maintains never happened.

The varying positions allowed India to trumpet its reprisal against Pakistan without forcing Islamabad to respond in a way that might spiral into a larger conflict.

Indian ministers lauded the airstrikes on Tuesday morning. “It was an act of extreme valour,” said Prakash Javadekar, the human resources development minister, in the first official acknowledgement of the operation.

Another minister, Vijay Kumar Singh, posted a picture on Twitter of an eagle with a snake in its talons. “They say they want to bleed India with 1,000 cuts,” he wrote. “We say that each time you attack us, be certain we will get back at you, harder and stronger.”

Though Pakistan downplayed the attacks, Khan, whose successful election campaign last year featured strident promises to stand up to India, could still face popular pressure to respond.

“Strategically, it is a disaster for Pakistan that India can keep doing this,” said Mosharraf Zaidi, a political analyst and columnist, referring to both Tuesday’s attack and the September 2016 strikes. “What does it say about Pakistan’s red lines that countries like India can keep violating our airspace or claim they have carried out surgical strikes?”

Sherry Rahman, a Pakistani senator and former ambassador the US, said the attack was aimed at Indian PM Narendra Modi’s re-election. “India is giving its own people a message with these strikes; this is for their electorate, the domestic voters,” Rahman said.

The Indian news agency Asian News International quoted Indian air force sources claiming 12 Mirage fighter jets had struck “a major terrorist camp” over the border with 1,000kg of explosives. The attack took place at about 3.30am, the agency claimed.

While exchanges of artillery and light weapons over the line are very common, intentional incursions by aircraft have not been publicly acknowledged since the two countries fought a war in 1971.

Military planes could be heard over Srinagar, the capital of Indian-controlled Kashmir, in the early hours of Tuesday morning. There has been a large troop buildup in the region in recent days and doctors have been advised to cancel leave and stockpile medicines.

Several convoys of trucks carrying heavy artillery were being transported on highways to northern Kashmir towards the line of control.

More than 300 separatist activists have been detained in recent days. Hours after the attack on Tuesday morning, officers from the National Investigation Agency raided the Srinagar homes of two veteran separatist leaders, Yasin Malik, who was among those detained at the weekend, and Mirwaiz Umar Farooq.