U.S. Secretary of State Marco Rubio called senior officials in India and Pakistan in an effort to defuse the crisis that followed last week's deadly attack in Kashmir, the State Department said.

Rubio urged Pakistan’s Prime Minister Shehbaz Sharif and Indian Foreign Minister Subrahmanyam Jaishankar to de-escalate tensions on Wednesday.

India has vowed to punish Pakistan after accusing it of backing the attack, which Islamabad denies. The nuclear-armed rivals have since expelled each other's diplomats and citizens, ordered the border shut and closed their airspace to each other. New Delhi has suspended a crucial water-sharing treaty with Islamabad.

Soldiers on each side have also exchanged fire along their de facto border, driving tensions between India and Pakistan to their highest point in recent years.

The region of Kashmir is split between India and Pakistan and claimed by both in its entirety. The two countries have fought two wars and one limited conflict over the Himalayan territory.

U.S. State Department’s Spokesperson Tammy Bruce said Rubio in his call with Jaishankar expressed sorrow over last week’s massacre. He also reaffirmed the U.S.’s "commitment to cooperation with India against terrorism,” Bruce said.

Jaishankar on Thursday said he discussed the last week’s massacre in Indian-controlled Kashmir’s Pahalgam, in which 26 tourists, mostly Hindu men, were killed, with Rubio, adding that “perpetrators, backers and planners” of the attack “must be brought to justice.”

Dozens of tourist resorts in Indian-controlled Kashmir are closed after deadly attack

Rubio also spoke to Sharif on Wednesday evening and “emphasized the need for both sides to continue working together for peace and stability in South Asia,” according to a Pakistani statement. It said Sharif rejected the Indian allegations and “urged the U.S. to impress upon India to dial down the rhetoric and act responsibly.”

Public anger has swelled in India and Prime Minister Narendra Modi has vowed to pursue the attackers “to the ends of the earth.” A Pakistani minister has said that Pakistan has “credible intelligence” that India is planning to attack it within days.

Indian and Pakistani troops have exchange fire over the past six nights, with each side blaming the other for firing first.

Tensions persist along India-Pakistan Kashmir border amid cross-border skirmishes

The Indian army in a statement on Thursday said it responded to “unprovoked” small arms fire from Pakistan in the Kupwara, Uri and Akhnoor sectors of Indian-controlled Kashmir. The previous day, Pakistan’s state-run media said Indian forces had violated the ceasefire agreement along the Line of Control by initiating fire with heavy weapons on troops in the Mandal sector of Pakistan-controlled Kashmir. The incidents could not be independently verified.

In the past, each side has accused the other of starting border skirmishes in the Himalayan region.