India’s Foreign Minister Subrahmanyam Jaishankar told U.S. Secretary of State Marco Rubio on Wednesday that those behind last week’s deadly attack in Kashmir must be held accountable, as the United States works to defuse rising tensions between India and Pakistan—two nuclear-armed rivals with a long history of conflict.

In back-to-back phone calls with Indian and Pakistani officials, Rubio urged both sides to de-escalate hostilities and cooperate in the aftermath of the April 22 massacre that left 26 people dead. According to the U.S. State Department, Rubio reaffirmed Washington’s commitment to supporting India’s fight against extremism while pressing Pakistan to assist in the investigation.

On social media, Jaishankar wrote that he told Rubio the “perpetrators, backers, and planners” of the Kashmir attack “must be brought to justice.”

Meanwhile, Pakistani Prime Minister Shehbaz Sharif appealed to the U.S. to encourage India to “dial down the rhetoric and act responsibly,” according to a statement released by his office.

The attack occurred in the Pahalgam region of Kashmir, where armed militants reportedly opened fire on a group of tourists, separating the men, asking for their names, and executing Hindu individuals at close range. Authorities confirmed that 26 people—most of them visitors—were killed in the assault.

India identified the three attackers, including two Pakistani nationals, as members of a long-running insurgency in Kashmir. Islamabad has denied involvement and called for an independent international inquiry into the incident.

Kashmir remains one of the world’s most volatile flashpoints, claimed in full by both Hindu-majority India and Muslim-majority Pakistan, though each controls only a portion of the region. The two countries have fought two wars over the territory, and tensions have remained high for decades. New Delhi has long accused Islamabad of supporting cross-border militancy in Indian-administered Kashmir—a charge Pakistan denies, saying it offers only moral and diplomatic backing to Kashmiri demands for self-determination.

In response to the latest attack, both nations have enacted retaliatory measures. India suspended the Indus Waters Treaty, a vital river-sharing agreement, while both sides shut down their airspace to each other’s airlines. Indian military officials also reported ongoing nightly cross-border gunfire over the past week, though no injuries have been confirmed.

Pakistan has not responded to requests for further comment on the matter.