At least 20 people were in Indian-administered Kashmir when gunmen opened fire on tourists, security sources told AFP, in the region's deadliest attack on civilians since 2000.
Prime Minister Narendra Modi decried the attack in Pahalgam as a "heinous act" and pledged that the attackers "will be brought to justice".
One security source put the death toll at 20; the second put it at 24 and the third at 26. All three spoke on condition of anonymity as they were not authorised to speak to the media.
The killings come a day after Mr Modi met in New Delhi with US Vice President JD Vance, who is on a four-day tour of India with his wife and children.
A tour guide in Pahalgam told AFP he reached the scene after hearing gunfire and had transported some of the wounded away on horseback.
Waheed, who gave only one name, said he saw several men lying dead on the ground, while a witness who requested anonymity said the attackers were "clearly sparing women".
Pahalgam lies 90km by road from the key city of Srinagar.
One security source said that foreign tourists were among those shot, but there was no official confirmation.
Other security sources and some Indian media reported that 26 people had died, an increase from the 24 that a senior local police officer had earlier told AFP.
No group has claimed responsibility, but rebels in the Muslim-majority region have waged an insurgency since 1989.
They are seeking independence or a merger with Pakistan, which controls a smaller part of the Kashmir region and, like India, claims it in full.
EU chief Ursula von der Leyen on Tuesday condemned the attack as a "vile terror attack" but said India's "spirit is unbreakable".
"The vile terror attack in Pahalgam today stole so many innocent lives," she said in a condolence message on X, formerly Twitter.
"Yet I know that India's spirit is unbreakable. You will stand strong in this ordeal. And Europe will stand with you," the European Commission president added.
Mr Vance offered condolences in a social media post, while President Donald Trump claimed that "the United States stands strong with India against terrorism".
Mr Modi, who is in Saudi Arabia, has cut short his trip to return home, foreign ministry officials said.
Males targeted
"The militants, I can't say how many, came out of the forest near an open small meadow and started firing," said the witness who asked not to be identified.
"They were clearly sparing women and kept shooting at men, sometimes single shot and sometimes many bullets, it was like a storm," said the man, who cares for horses that are popular with tourists in the area.
The witness said dozens of people fled as the gunmen opened fire.
"They all started running around in panic", he added.
Jammu and Kashmir Chief Minister Omar Abdullah said that "the attack is much larger than anything we've seen directed at civilians in recent years", with the death toll still uncertain.
"This attack on our visitors is an abomination," he added in a statement.
"The perpetrators of this attack are animals, inhuman and worthy of contempt."
Holiday destination
Medics at a hospital in Anantnag said they had received some of the wounded, including with gunshot wounds.
India has an estimated 500,000 soldiers permanently deployed in the territory, but fighting decreased since Mr Modi's government revoked Kashmir's limited autonomy in 2019.
"Their evil agenda will never succeed. Our resolve to fight terrorism is unshakable and it will get even stronger," Mr Modi said in a statement.
In recent years, the authorities have promoted the mountainous region as a holiday destination, both for winter skiing, and to escape the sweltering summer heat elsewhere in India.
Around 3.5 million tourists visited Kashmir in 2024, the majority domestic visitors.
In 2023, India hosted a G20 tourism meeting in Srinagar under tight security in a bid to show that what officials call "normalcy and peace" were returning after a massive crackdown.
A string of resorts are being developed, including some close to the heavily militarised de facto border that divides Kashmir between India and Pakistan.
India regularly blames Pakistan for backing gunmen behind the insurgency.
Pakistan denies the allegation, saying it only supports Kashmir's struggle for self-determination.
The worst attack in recent years took place in Pulwama in February 2019, when insurgents rammed a car packed with explosives into a police convoy killing 40 and wounding at least 35 others.
The deadliest recent attack on civilians was in March 2000, when 36 Indians were killed. That attack occurred on the eve of a visit by former US president Bill Clinton.
