The armies of India and Pakistan squared off along their common border as tension mounted following last week's suicide attack on the New Delhi parliament.
Indian and Pakistani troops also traded artillery and small arms fire over their disputed border in northern Kashmir state, the first such exchange since Delhi accused Islamabad-backed militant groups of attacking its parliament on December 13th. Thirteen people, including the five attackers, died in the assault.
Pakistan has dismissed India's allegation as baseless and inflammatory and moved its strike units up to the Jammu border. Supported by armoured formations, around four divisions (over 80,000 Pakistani troops) are believed to have fortified their positions in anticipation of an Indian attack.
But a Pakistani military spokesman, Maj-Gen Rashid Qureshi, dismissed Indian reports of a troop build-up. "It is possible that in order to justify their own build-up, they [India] might be shifting the blame on to Pakistan," he said.
Around a third of India's 1.2 million strong army is permanently based in Kashmir to guard the border and engage in counter-insurgency operations, fighting Muslim militants who have been waging a civil war for an independent homeland for over 12 years.
Military sources said India too was "re-organising" its armoured columns along the border, redeploying troops and commandeering trains to ferry soldiers to the frontier from across the country.
The Indian Prime Minister, Mr Atal Behari Vajpayee, said India was keeping its options open in response to the attack on parliament.
Referring to US appeals for restraint, Mr Vajpayee said India had already reached "the pinnacle of tolerance" and would tackle terrorism alone, keeping its own security interests uppermost. "We don't expect anyone to fight for us. We don't expect anyone to jump into the battlefield for us.
We will fight on our own " a combative Mr Vajpayee declared.
"Those counselling us to show restraint should also give the same advice to our neighbour," he said while rejecting Pakistan's offer to conduct a joint investigation into the attack on parliament.
There is no question of a joint inquiry, Mr Vajpayee said.
"I have acted in whatever manner it was appropriate to act." India's chief of army staff, Gen S. Padmanabhan said. I am not going to be stampeded into any kind of action. We are not a flappy army but a very confident army. We know precisely what we want to do."
India claims to have "irrefutable" evidence that the attack on parliament was carried out jointly by two Pakistan-based militant groups - Lashkar-e-Taiba and Jaish-e-Mohammad - at the behest of Pakistan's Inter-Services Intelligence (ISI) agency.
The US has reiterated its appeal to Delhi to defuse tension.