(Adds Indian foreign minister's comment during Paris visit)
By Katharine Houreld
ISLAMABAD, Jan 10 (Reuters) - Indian troops killed a Pakistani soldier on Thursday in the disputed region of Kashmir, the Pakistani army said, extending the worst outbreak of violence in the area since the nuclear-armed neighbours agreed a ceasefire nearly a decade ago.
In the third fatal attack in five days, the Pakistani was killed by "unprovoked" Indian fire while manning a post in the Battal sector of Kashmir, which is split between the two sides by a heavily fortified border known as the Line of Control (LoC), the army spokesman said.
A Pakistani soldier was killed Sunday, and two Indian soldiers were killed and mutilated on Tuesday, their respective armies said. The two sides have lodged diplomatic protests.
India and Pakistan have fought three wars since becoming independent from Britain in 1947, two of them over the Himalayan region of Kashmir.
Relations had shown signs of improving in the past year after souring again in 2008 when Pakistan-based gunmen attacked India's financial capital of Mumbai, killing 166 people.
Both governments have expressed anger over the latest Kashmir attacks even as senior officials sought to calm fears that right-wing groups could seize the opportunity to derail years of diplomatic rapprochement.
Pakistani Foreign Minister Hina Rabbani Khar said she was "unpleasantly surprised" by Indian accusations against Pakistan, but tried allay fears that the stand-off could escalate.
"The Pakistan government and the Pakistani people have demonstrated a deep and abiding commitment to normalise and improve relations with India and to really start a journey of trust-building," she said.
Indian Foreign Minister Salman Kurshid, asked about the violence during a visit to Paris, told reporters: "It's extremely shocking and unacceptable..., we've even used the word barbaric. I can't imagine that anyone would disagree with that on either side of the border. To take responsibility or not is another matter. We are still arguing about that."
He said India was pushing Pakistan for answers and needed to analyse the situation more carefully before commenting further.
"While we want some redress and we want some transparency from the accountability office, we do believe that whoever has tried to derail a wholesome peace process shouldn't succeed."
Pakistani villagers living near the Line of Control said it had mostly been quiet in recent years although sporadic shooting was common. The recent surge in violence was unexpected.
"On Sunday there was intense shelling between Indian and Pakistan troops. It was many years since we've seen such a thing," said Tehzeeb un Nisa, head of the administration in Darra Haji Pir, where the Pakistani soldier was killed Sunday.
Indians said tensions had been building over the past year.
"There's been increase in ceasefire violations and infiltration attempts in 2012 over 2011," Shivshankar Menon, India's national security adviser, told a media conference in New Delhi on Thursday. "We have condemned (the killings of Indian soldiers) ... I hope it never happens again."
Pakistan called for the United Nations to investigate the recent attacks. A team monitoring the ceasefire has been in place for around 60 years.
Pakistan reported Sunday's killing to the United Nations.
"We are certainly not going to agree to internationalise the issue or allow the United Nations to hold an inquiry. That demand is obviously rejected out of hand," said Indian Finance Minister P. Chidambaram.
Indian officials said Pakistani militants could be to blame. They said the founder of banned militant group Lashkar-e-Taiba had recently visited Kashmir, potentially to incite violence.
"We have been informed Hafiz Saeed entered the PoK (Pakistan Occupied Kashmir) area and had talks with some people," said Indian Home Minister Sushil Kumar Shinde.
Hafiz Saeed is suspected of masterminding the Mumbai attack.
The United States has offered $10 million for information leading to his arrest and conviction.
Editing by Jeremy Laurence/Mark Heinrich