At least nine civilians were killed and nine injured in Pakistan-administered Kashmir when an Indian artillery shell hit a passenger bus in the disputed region on Wednesday, Pakistani officials said.

"The passenger bus was attacked by Indian shelling at 8.30 in the morning, resulting in the death of nine people on-board," DSP Neelum Valley Mqsood told Al Jazeera.

"The ambulance heading to the site came under attack as well and locals arranged transportation for those injured, taking them to the hospital in private cars."

Local administration official Sardar Waheed said firing between the two countries was continuing and that was preventing ambulances from reaching the scene.

Indian officials did not comment on the deaths but a military spokesperson said the Pakistan army initiated "indiscriminate" firing on Wednesday morning on Indian army posts in the Bhimber Gali, Krishna Ghati and Nawshera sectors.

The incident comes a day after India said three of its soldiers had been killed by Pakistani troops and threatened "retribution".

Pakistan and India have been trading fire recently in the Himalayan region, which is divided between the two nuclear-armed neighbors and claimed by both in its entirety.

Tension has escalated since armed fighters attacked an Indian army base in Kashmir in September, killing 19 Indian soldiers.

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

PHOTO CAPTION

Map locating Kashmir

Al-Jazeera