NEW DELHI (AFP) — New Delhi closed its airspace to Pakistani airplanes on Wednesday after Islamabad banned Indian planes from overflying, the latest tit-for-tat measure as relations between the nuclear-armed rivals spiral into a tailspin.

New Delhi accuses Islamabad of backing the deadliest attack in years on civilians in Indian-administered Kashmir on 22 April, in which 26 men were killed.

Islamabad has rejected the charge, and both countries have since exchanged gunfire in Kashmir, diplomatic barbs, expelled citizens and ordered the border shut.

Pakistan closed its airspace to Indian aircraft on 24 April, while India took a similar measure on Wednesday evening, with the ban to last until 23 May, the government notice said.

The notice to air operators said that Indian airspace was not available for Pakistani registered or leased aircraft — “including military flights.”

Indian Prime Minister Narendra Modi gave the military “complete operational freedom” to respond to the attack during a closed-door meeting on Tuesday, a senior government source told Agence France-Presse.

Pakistan’s government has denied any involvement in the shooting and vowed that “any act of aggression will be met with a decisive response.”

Schools shut

Meanwhile, authorities in Pakistan-administered Kashmir shut more than 1,000 religious schools Thursday over fears of possible military action from India in retaliation for last week’s deadly attack.

“We have announced a 10-day break for all madrassas in Kashmir,” said Hafiz Nazeer Ahmed, head of the local religious affairs department.

A department source said it was “due to tensions at the border and the potential for conflict.”

“For one week we have been living in constant fear, particularly concerning the safety of our children,” Iftikhar Ahmad Mir, a 44-year-old shopkeeper in Chakothi on the Line of Control, told Agence France-Presse.

“We make sure they don’t roam around after finishing their school and come straight home.”

Emergency services workers in Muzaffarabad, the main city in Pakistan-administered Kashmir, have also begun training schoolchildren on what to do if India attacks.

“We have learned how to dress a wounded person, how to carry someone on a stretcher and how to put out a fire,” said 11-year-old Ali Raza.

Muslim-majority Kashmir, a region of around 15 million people, is divided between nuclear-armed Pakistan and India which have fought several wars over the disputed territory.

About 1.5 million people live near the ceasefire line on the Pakistani side, where residents are readying simple, mud-walled underground bunkers — reinforced with concrete if they could afford it.