ARNIA, India/MUZAFFARABAD, Pakistan: Islamabad said on Thursday it was capable of responding “befittingly” to Indian border shelling, and warned against an escalation of the worst fighting between the nuclear-armed rivals in more than a decade.

Nine Pakistani and eight Indian civilians have been killed since both sides’ security forces started heavy shelling more than a week ago along a 200-km stretch of border in the disputed, mostly Muslim region of Kashmir.

More were injured on Thursday. Both countries accused each other of starting the latest hostilities that have hit heavily populated civilian areas. India says it will not talk to Pakistan or stop firing until its neighbor backs down first.

“We do not want the situation on the borders of two nuclear neighbors to escalate into confrontation,” the Pakistan Ministry of Defense said in a statement. “India must demonstrate caution and behave with responsibility.”

India earlier warned Pakistan it would pay an “unaffordable price” if it persisted with shelling and machine-gun fire across a heavily populated border area in the lowlands of Kashmir. Pakistan’s Maj. Gen. Khan Tahir Javed Khan, responsible for the section of the border where the violence has broken out, said that India had fired 20,000 shells so far this year, compared to just 200 in 2012. He also said he had been trying to meet his Indian counterpart since the exchanges of fire began, but they would not return his calls. Since late on Wednesday, 13 people including three Indian border guards were injured in firing, a senior Indian police official in Kashmir said.

India Premier Narendra Modi said: “I don’t need to speak, our guns will do it. We have responded with courage to cease-fire violations.”

UN Secretary-General Ban Ki-moon expressed concern over the escalation of violence. “The secretary-general is concerned about the recent escalation of violence along the line of control between India and Pakistan. He deplores the loss of lives and the displacement of civilians on both sides,” said United Nations spokeswoman Vannina Maestracci.

The UN chief “encourages the governments of India and Pakistan to resolve all differences through dialogue...,” the spokeswoman said.