ISLAMABAD, May 26 (AFP) - Pakistan placed its armed forces on high alert Wednesday and warned India it would retaliate unless its arch-rival, which launched air strikes in the disputed Kashmir region, backed off. The two newest nuclear states traded threats in the wake of more than two weeks of fierce cross-border artillery duels in Kashmir that took a new turn with Wednesday's aerial bombardment by India. India said its air force had launched the attack in a bid to flush out what it described as Pakistan-backed guerrillas entrenched on the heights in Kargil and Daras sectors. It warned it would take "appropriate action" if Pakistani forces intervened in the air strikes. Pakistan, which denies backing an insurgency into India's only Moslem-majority state, blamed India for fuelling border tension in the volatile region. A military spokesman told reporters Pakistani forces were on "high alert" after the unprecedented Indian air strikes in the divided territory. "Pakistan reserves the right to retaliate in whatever manner considered appropriate," he said. Continued Indian violations of Pakistan's territory could "snowball into a bigger conflict," he said. A number of bombs landed on the Pakistan side during Wednesday's aerial bombardment by the Indian air force in Kargil and Daras sectors in Kashmir, but there was no damage, he said. Pakistan has taken "very serious notice" of the situation and a protest would be lodged with India. The spokesman said the first of the Indian air strikes came at dawn and lasted half an hour. Another round was launched later and helicopter gunships were also seen in operation, he said. He said the Indian army had suffered more than 100 casualties since its abortive May 6 attempt to seize a Pakistani post in the area near the Siachen glacier, the world's highest battlefield. He said the latest Indian move appeared to be aimed at capturing territory on the Pakistani side of the border dividing Kashmir. Prime Minister Nawaz Sharif chaired a high-level meeting late Tuesday on the growing military crisis, which was also attended by top military brass, official sources said. Foreign Minister Sartaj Aziz blamed India for the escalation along the 720-kilometer Line of Control, which separates the Indian and Pakistani controlled zones of disputed Kashmir. The neighbours have gone to war twice over the Himalyan region, of which India holds two-thirds and Pakistan the remaining northern third. India has consistently accused Pakistan of fuelling a Moslem separatist campaign that has claimed about 25,000 lives since 1989. Pakistan denies the charge, but vows political and moral support for the "legitimate freedom struggle." Rival troops along the Line of Control have been trading heavy artillery fire in Kargil and some other sectors since May 9, prompting a call by UN Secretary General Kofi Annan for a halt to the clashes. "The escalation at the Line of Control is against the spirit of the Lahore Declaration" signed by Sharif and his Indian counterpart Atal Behari Vajpayee in February, Aziz told reporters. "We have called for restraint on both sides. We do not know why they (Indians) are escalating the situation," Aziz said before the news that the Indian air force had launched strikes in Kargil. The minister said India's deputy high commissioner was summoned to the foreign office two days ago and was told that "the situation must not be escalated." Of the artillery duels, Aziz said: "We have just retaliated when our positions are attacked and we only defend ourselves."  