Tensions have been elevated since a suicide car bombing by Pakistan-based militants in Indian-controlled Kashmir killed at least 40 Indian paramilitary police on Feb. 14, but the risk of conflict rose dramatically on Tuesday when India launched an air strike on what it said was a militant training base.

The attack targeted the Jaish-e-Mohammed militant, the group that claimed credit for the suicide attack. But while India said a large number of JeM fighters had been killed, Pakistani officials said the Indian airstrike was a failure and inflicted no casualties.

On Tuesday, evening Pakistan began shelling using heavy calibre weapons in 12 to 15 places along the de facto border in Kashmir, known as the Line of Control (LoC), a spokesman for the Indian defence forces said on Wednesday.

"The Indian Army retaliated for effect and our focused fire resulted in severe destruction to five posts and number of casualties," the spokesman said.

Five Indian soldiers suffered minor wounds in the shelling that ended on Wednesday morning, he added.

"So far there are no (civilian) casualties but there is panic among people," said Rahul Yadav, the deputy commissioner of the Poonch district where some of the shelling took place.

"We have an evacuation plan in place and if need arises we will evacuate people to safer areas,” he said.

Local officials on the Pakistani side said at least four people had been killed and seven wounded, though it was unclear if the casualties were civilian or military.

India has also continued its crackdown on suspected militants operating in Kashmir, a mountainous region that both countries claim in full but rule in part.

On Wednesday, security forces killed two Jaish militants in a gun battle, Indian police said.

HEIGHTENED SECURITY

Pakistan has promised to retaliate to Tuesday's air strikes, and security across India has been tightened. The two countries have fought three wars since independence from British colonial rule in 1947 and went to the brink a fourth in 2002 after a Pakistani militant attack on India's parliament.

In Punjab, an Indian state that borders Pakistan, security alerts are in place in several districts, according to media reports.

Schools within 5 kilometres (3 miles) of LoC were closed in one district in Kashmir.

In Mumbai, India's financial capital, there was a visible increase in security levels for a city that has suffered numerous militant attacks in the past.

US Secretary of State Mike Pompeo spoke separately with the foreign ministers of India and Pakistan and urged them to avoid "further military activity" following Tuesday's airstrike.

"I expressed to both ministers that we encourage India and Pakistan to exercise restraint, and avoid escalation at any cost," Pompeo said in a statement on Wednesday.

"I also encouraged both ministers to prioritize direct communication and avoid further military activity," he said.

Both China and the European Union have also called for restraint. On Wednesday New Zealand's foreign minister Winston Peters also voiced concern over the escalation in tensions.