LAHORE, Pakistan — India fired attack drones into Pakistan on Thursday, killing at least two civilians, the Pakistani military said. India, meanwhile, accused its neighbor of attempting its own attack, as tensions soared between the nuclear-armed rivals.

India acknowledged that it targeted Pakistan’s air defense system, and Islamabad said it shot down several of the drones. India said it “neutralized” Pakistan’s attempts to hit military targets. It was not possible to verify all of the claims.

The exchanges came a day after Indian missiles struck several locations in Pakistan, killing 31 civilians, according to Pakistani officials. New Delhi said it was retaliating after gunmen killed more than two dozen people, mostly Hindu tourists, in India-controlled Kashmir last month. India accused Pakistan of being behind the assault. Islamabad denies that.

Both sides have also traded heavy fire across their frontier in disputed Kashmir, and Pakistan claimed it killed scores of Indian soldiers. There was no confirmation from India.

Late Thursday in Indian-controlled Kashmir, residents of the city of Jammu reported explosions and sirens, followed by a blackout.

India’s Headquarters of the Integrated Defence Staff, a central coordinating arm for all Indian armed forces, said military stations in Jammu, Udhampur and Pathankot were targeted by Pakistan using missiles and drones. It said the attacks were repelled and no casualties were reported.

Shesh Paul Vaid, the region’s former director-general of police, told The Associated Press that the Jammu Airport likely was also under attack and that some of the 50 loud explosions he heard likely were because “our defense system is at work.”

Jammu and Udhampur are close to the Line of Control, the de facto border that divides the Kashmir region between India and Pakistan. Pathankot is in India’s Punjab state.

Sirens were also heard in some parts of the region’s main city of Srinagar, residents said. It was followed by blackout in the city and other parts of the region.

The state-run Pakistan Television denied reports of military strikes in Indian-controlled Kashmir, calling them “false, baseless, and fabricated.”

Pakistan’s Prime Minister Shehbaz Sharif has vowed to avenge the deaths in India’s missile strikes, raising fears that the two countries could be headed toward another all-out conflict. Leaders from both nations face mounting public pressure to show strength and seek revenge.

U.S. Secretary of State Marco Rubio spoke Thursday to the Pakistani prime minister and India’s External Affairs Minister Subrahmanyam Jaishankar, urging both sides to de-escalate the situation, the U.S. State Department said.