By Asad Hashim and Fayaz Bukhari

ISLAMABAD/SRINAGAR, India (Reuters) - Shelling across the border between India and Pakistan killed two Pakistani civilians, an Indian soldier and a boy, military officials from the two sides said on Monday, as tension between the nuclear-armed neighbors simmers.

Pakistan's military said the shelling hit the sectors of Harpal, Pukhlian and Charwah along the disputed "working boundary", which separates Pakistan's Punjab province from Indian-administered Kashmir's Jammu region.

India's military said the firing occurred in the Pura, Pargwal and Kanachak sectors.

Both countries have claimed the disputed Kashmir region in full since partition and independence from the British in 1947, but administer separate portions of it. They have fought two of their three wars over the territory.

Tensions have been strained since July, when Indian forces killed a young Kashmiri fighter, prompting mass protests in Indian-administered Kashmir. The resulting crackdown by security forces has seen at least 80 Kashmiri protesters killed.

Relations plummeted even further in September, when gunmen stormed an Indian military base in Uri, killing 18 Indian soldiers, the largest such attack in 14 years.

India blamed Pakistan for the attack, and in response said it had launched "surgical strikes" across the de facto border in Kashmir on Sept 29 to target Kashmiri fighters based there. Pakistan denied any incursion had occurred on its territory.

Pakistan's military said a one-year-old child was among the dead in Pakistan in the village of Janglora. Pakistani forces responded to the Indian firing and an exchange of fire continued through the night.

Fifteen civilians were wounded in the firing, Pakistan said.

In India's Jammu region, a Border Security Force (BSF) soldier was killed by the Pakistani firing, while another was wounded, a BSF spokesman told Reuters. A boy, one of five civilians also injured, later died of his wounds, he said.

(Writing by Asad Hashim; Editing by Drazen Jorgic and Toby Chopra)