India and Pakistan moved closer to all-out war early Saturday as the Pakistani military accused India of attacking at least three of its air bases, and then reported that it had retaliated by targeting Indian air bases and a missile storage site.

The reported exchange of strikes was a sharp escalation between the nuclear-armed neighbors four days into an armed confrontation that began Wednesday.

Pakistan said India had targeted its bases with air-to-surface missiles. Among the bases that came under attack, Pakistan said, was a key installation near the capital, Islamabad. Witnesses in Rawalpindi, a nearby garrison city, reported hearing at least three loud explosions near the Noor Khan air base, with one describing a “large fireball” visible from miles away.

“Now, you just wait for our response,” Lt. Gen. Ahmed Sharif Chaudhry, the Pakistani military’s chief spokesperson, said in a televised statement. He accused India of pushing the region toward a “dangerous war.”

Shortly after the reported Indian strikes, Pakistani officials said they had launched a retaliatory action targeting several locations in India, including the Udhampur and Pathankot air bases and a missile storage facility.

“An eye for an eye,” the Pakistani military said in a statement. It said it was calling its campaign against India “Operation Bunyan al-Marsus,” which means a firm and compact structure.

After several days of shelling and drone attacks, India and Pakistan, old enemies, are engaged in their most expansive military conflict in decades. And they are using new tools of war to enhance their ability to attack and spy on each other.

On Friday, Indian defense officials said Pakistan’s military had attempted aerial intrusions in 36 locations with “300 to 400” drones to test India’s air-defense system.

A day earlier, Pakistani military officials said they had shot down 25 drones belonging to India, including in Karachi and Rawalpindi, the headquarters of Pakistan’s main intelligence body. Pakistani officials also told U.S. officials that India was engaging in “drone terrorism” by targeting civilian areas, according to a statement. India has not commented on the drones.

Although many countries now have drones in their arsenals, this is the first time the unmanned aerial vehicles are being used by the two countries against each other. The use of drone warfare may have been inevitable, but it could reshape the way the world views hostilities between India and Pakistan, much as it did after the two countries became nuclear powers in the 1990s.

The conflict began after militants killed 26 people last month in India-controlled Kashmir. India accused Pakistan of being behind the attack and vowed to take military action. Pakistan has denied involvement.

The conflict has escalated since Wednesday, when India conducted airstrikes on Pakistan. Since then, the two countries have been locked in an intensifying exchange of gunfire, drone attacks, claims, counterclaims and misinformation.

Diplomatic pressure, notably from Saudi Arabia and the United Arab Emirates, has not worked. And the two countries have largely ignored statements from the United States and Europe calling for calm.

In a statement Friday, foreign ministers from the Group of 7 industrialized nations urged “maximum restraint from both India and Pakistan” and warned that “further military escalation poses a serious threat to regional stability.”

Raj Shukla, a retired commander in the Indian army, said India had been building its supply of drones.

India and Pakistan have been developing their respective drone-building industries in recent years, and both import drones from foreign allies. But neither country appears to have any that can carry nuclear warheads, said James Patton Rogers, a drone warfare expert at Cornell University. And while he called the conflict “incredibly worrying,” he also noted that drones generally are used as the lowest possible escalatory step in a conflict.