India and Pakistan have held talks aimed at defusing tensions along the Line of Control that divides Indian- and Pakistani-administered Kashmir.
Pakistan denies its soldiers fired any shells
India accused Pakistan of violating a ceasefire along the de facto border by firing shells into Indian-administered territory on Tuesday.
Pakistan denied the allegation, saying its soldiers had no role in the firing.
A ceasefire has been in place along the Line of Control since November 2003. Peace talks began last year.
Top Indian and Pakistani army commanders spoke by telephone on Wednesday and discussed the incident.
"We expressed our concern and the Pakistani commander promised to investigate the incident," Lt Gen BS Thakur, deputy chief of the Indian army, told reporters.
"There is going to be a series of discussions on this and I am sure that with the kind of understanding that exists between the two armies, there will be a better understanding and restraint on both sides."
The Indian army says Pakistan may have fired the shells as cover for infiltration by militants fighting against Indian rule.
Lt Gen Thakur said 60mm and 82mm mortars were fired in three salvoes, at
1830, 1925 and 2000 local time.
He said the shells were of the type used by Pakistan's army, but added that 82mm shells were also used by militants.
An army spokesman said a young girl was wounded in the firing into Poonch district, 250km (160 miles) north of Jammu, the winter capital of Indian-administered Kashmir.
"This is certainly a violation of ceasefire. This has happened for the first time [since] the ceasefire," an Indian army spokesman, Lt Col RK Chibber, told Reuters news agency earlier on Wednesday.
"We have maintained restraint."
Pakistani military spokesman Maj Gen Shaukat Sultan said its soldiers had heard some sounds of mortar firing, but they had no role in it.
"No-one from Pakistan has fired and there is no ceasefire violation by Pakistan," he told the AFP news agency.
Pakistani foreign ministry spokesman Masood Khan told Reuters that its soldiers "heard a blast... on Tuesday evening from the side of Indian-held Kashmir but we don't know the source".
The firing came after Indian security forces said they had shot dead four suspected militants on the Line of Control in Poonch district earlier on Tuesday.
Militant separatists have been fighting Indian rule in Kashmir, which is claimed by both Pakistan and India, since 1989. About 40,000 people are reported to have been killed in the fighting.
India and Pakistan have fought two wars over Kashmir since independence.
They embarked on a peace process in January last year to try to resolve their differences, including those over Kashmir.
India pulled back several thousand troops from Indian-administered Kashmir in November because of a perceived decrease in violence.
It is estimated to have between 180,000 and 350,000 soldiers in the state, including paramilitary special forces.