Gen. Bikram Singh's strong words are a clear message that India believes the Jan. 8 attack was a deliberate provocation and not an unintentional skirmish of the kind that often breaks out along the Line of Control, the de facto border between the two archrivals in the Himalayan territory.
Pakistan did not immediately respond to the comments, which are likely to raise tensions further.
The tit-for-tat fighting began Jan. 6 when Pakistan accused Indian troops of raiding an army post and killing a soldier. India denied attacking the post, and said its troops fired across the border in response to Pakistani shelling that destroyed a home on the Indian side.
On Jan. 8, India claimed Pakistani soldiers, taking advantage of heavy fog, crossed the border and killed two Indian soldiers and beheaded one of them.
Pakistan denies India's allegations and has suggested U.N. monitors in the region conduct an inquiry - a call that India rejected, saying it didn't want to internationalize the issue.
"The attack on Jan. 8 was premeditated, a pre-planned activity. Such an operation requires planning, detailed reconnaissance," Singh told reporters. He said India reserved the right to retaliate at a "time and place of its choice."
Singh urged his troops to be "aggressive and offensive in the face of provocation and fire" from Pakistan. He said the alleged beheading of the Indian soldier was "unacceptable and unpardonable" and accused Pakistan of violating the "ethics of warfare."
Tensions escalated further on Jan. 10 when Pakistan said Indian troops fired across the border and killed another one of its soldiers. The Pakistani army said the shooting was unprovoked, while the Indian military said its troops were responding to fire from across the frontier.
Both countries accused each other of violating a 2003 cease-fire and have summoned their envoys to lodge protests.
Singh spoke hours before Indian and Pakistani military commanders met to defuse tensions along the Line of Control.
The meeting between the local commanders of the two armies in the Poonch region of Indian-controlled Kashmir lasted about half an hour, said Col. R.K. Palta, an Indian army spokesman.
Brig. Bipin Bakshi, a senior Indian army officer, said India raised the issue of repeated cease-fire violations by Pakistani troops "and conveyed our strong protest regarding the barbaric act of the mutilation of our soldier."
Bakshi said Pakistani army officers refused to acknowledge that their troops initiated any violations of the cease-fire, staged any raids or killed any soldiers.
He said Pakistan accused the Indian army of violating the cease-fire and crossing the military line.
The cease-fire over Kashmir has largely held for about a decade, despite periodic firing across the de facto border that sometimes causes casualties.
The two countries have fought three major wars since Pakistan's birth after British colonial rule of India ended in August 1947. Two of the wars have been over Kashmir, which both countries claim in its entirety. The wars have left about one-third of Kashmir with Pakistan and the rest with India.