India's Prime Minister Narendra Modi has warned Pakistan to expect a strong response to a car bomb attack that killed 44 paramilitary policemen in Kashmir.
The car bomb attack on a security convoy on Thursday was the worst in decades of insurgency in the disputed region.
India said it had "incontrovertible evidence" of Pakistani involvement - though that was quickly denied by Islamabad.
"We will give a befitting reply, our neighbour will not be allowed to de-stabilise us," Mr Modi said in a speech on Friday, after meeting security advisers to discuss options.
The attack comes months before national elections in India.
The Pakistan-based Islamist militant group Jaish-e-Mohammad (JeM) claimed responsibility soon after a suicide bomber rammed an explosives-laden car into a bus carrying police personnel.
India has for years accused Muslim Pakistan of backing separatist militants in divided Kashmir, which the neighbours both claim in full but rule in part. Pakistan denies that, saying it only offers political support to the Himalayan region's suppressed Muslim people.
The White House urged Pakistan "to end immediately the support and safe haven provided to all terrorist groups operating on its soil".
Pakistan is due to host peace talks next week between the Afghan Taliban and the United States as part of efforts to seek a political settlement to the Afghan war, but escalating tensions with India could divert Pakistan's attention.
As outrage and demands for revenge flooded Indian social media, one of the most senior figures in the Hindu nationalist-led government, Arun Jaitley, told reporters India would work to ensure the "complete isolation" of Pakistan.
The first step, he said, would include removing most favoured nation (MFN) trade privileges that had been accorded to Pakistan, though annual bilateral trade between the countries is barely US$2 billion.
The last major attack in Kashmir was in 2016 when Jaish militants raided an Indian army camp, killing 20 soldiers.
Indian Foreign Secretary Vijay Gokhale summoned Pakistan's ambassador, Sohail Mahmood, and issued a demarche demanding Pakistan take verifiable action against Jaish.
India also recalled its ambassador in Pakistan for consultations, a government source said.
Crowds gathered in Jammu, the Hindu-dominated part of Jammu and Kashmir state, demanding stronger action against Pakistan.
A curfew was briefly imposed in Jammu after crowds overturned and set fire to some vehicles.
Protesters were also marching to the Pakistani embassy in New Delhi.