MUZAFFARABAD, Pakistan (Reuters) - Indian shelling across the frontier into Pakistani-controlled Kashmir hit a bus, killing at least nine people, and three Pakistani soldiers were killed in cross-border firing, Pakistani officials said on Wednesday.

India, in a statement, expressed grief at Pakistani civilian casualties but said: “Retaliatory firing by Indian troops has only been carried out targeting locations from where Pakistan has initiated ceasefire violations on Indian posts.”

Describing the bus incident, Pakistani police official Jamil Mir put the number of dead at nine. He told Reuters four bodies were taken to a nearby hospital and five were still trapped in the bus.

Pakistan also said its military killed seven Indian soldiers on Wednesday.

Following the incident, Pakistan said it had summoned the Indian Deputy High Commissioner, J.P. Singh.

Pakistan’s military media wing, ISPR, put the death toll from the bus shelling at seven, adding three Pakistani soldiers were killed “while responding to Indian unprovoked firing.”

ISPR said: “We reserve the right to respond at the place and time of our choosing.”

Lawat, where the bus was hit, is 100 km (60 miles) northeast of Muzaffarabad, the capital of Pakistani-held Kashmir, in the upper belt of the Neelum Valley that straddles the de facto border dividing Kashmir between India and Pakistan.

An Indian military spokesman said the Pakistani Army initiated “indiscriminate” firing on Wednesday on Indian Army posts in Bhimber Gali, Krishna Ghati and Nawshera sectors.

Relations between nuclear-armed neighbors Pakistan and India have been strained for several months, while cross-frontier shelling has intensified leading to the deaths of civilians and soldiers stationed along the disputed frontier.

Kashmir lies at the heart of the tension. The countries have fought two of their three wars over the region since partition and independence from Britain in 1947.