They said the atmosphere along the border areas was 'tense' and a high alert is in place along this region of the Indo-Pak international border.
The sources said the Pakistani side, which spoke to the Border Security Force officials in the noon over phone, 'denied any hand' in the killing of Head Constable Narender Singh on September 18.
The Indian side termed the act as 'unsoldierly'.
It was informed that Pakistani troops 'shot and killed' the BSF trooper, they said.
They added that on getting this response, the BSF told the other side that any future misadventure on the India-Pakistan border will be the responsibility of the Pak Rangers.
"A brief phone call talk took place between the two sides this noon. When it was brought to the notice of Pakistan that they had killed the jawan by resorting to unprovoked fire, they flatly refused any hand of their troops in the incident," a senior official said.
This was the second round of protest that the BSF registered with their counterparts in the last over three days over the killing and throat slitting of their jawan who along with seven others had gone beyond the border fence in the Ramgarh sector as part of a elephant grass (sarkanda) cutting patrol.
The official said the force has issued a 'high alert' to all its forward locations on the 192-km-long frontier in Jammu in the backdrop of this incident which is suspected to be 'handiwork of a probably a pair of troops from the other side'.
The force, they said, has also observed the movement of helicopters and drones in the forward locations across the border in Jammu and hence border posts and patrols have been asked to remain extra vigilant, they said.
The force has also sought, they said, for a sector commander-level (Deputy Inspector General rank level) talks between the two sides in Jammu to thrash out issues but has not received any positive response.
They added that various field formations of the force have been receiving 'spoof calls' from across the border where people masquerading as government intelligence operatives or journalists are wanting to seek details about the incident.
Over a dozen calls have been received over the last two days on the personal and official numbers of field officers and it is suspected that the calls are being made from across the border, they said.
Meanwhile, Union Home Minister Rajnath Singh has told the BSF to take strongest possible action against the Pakistani troops who slit the BSF jawan's throat, officials said on Thursday.
This was conveyed to the top brass of the border guarding force which is deployed along the highly volatile Indo-Pak border.
The home minister told top officials of the BSF in no uncertain terms that the strongest possible action should be taken against the Pakistani troops involved in Tuesday's incident, a home ministry official, privy to the development, said.
The BSF jawan's throat was slit and his body bore multiple bullet injuries. The missing trooper was found killed by Pakistani troops in the Jammu region, in a first-of-its-kind barbaric act against Indian forces along the International Border.
Another official said the BSF is expected to take some 'pro-active' action against the Pakistan Rangers to 'avenge' the mutilation of the jawan's body.
In an atmosphere of anger and gloom, a huge gathering on Thursday bid a tearful adieu to BSF jawan Narender Singh, in Sonipat.
The mortal remains of BSF Head Constable Narender Singh were cremated with full state honours at his native Thana Kalan village in Haryana's Sonipat district.
Slogans of 'Bharat Mata ki Jai', Narender Singh Amar Rahe' rent the air as the body, wrapped in a tricolour, reached the village in the morning.
Several villagers chanted slogans against Pakistan. Family members and locals demanded that Pakistan should be taught a lesson for the "barbaric" act.
The funeral pyre was lit by his elder son Mohit.
"We are proud of our father for laying down his life for the nation. His death should be avenged," said a teary-eyed Mohit.
"Not everyone gets a chance to be draped in the tricolour...But we just cannot keep feeling proud. We will feel proud again, when another death takes place. We demand action against Pakistan," he said.
He also demanded that the concerned authorities provide whatever help the family needs.
Other family members also appealed to the Centre to act tough against Pakistan.
Several prominent persons inlcuding Haryana minister Krishan Bedi, Congress leader Randeep Singh Surjewala and senior officials of BSF were also among the mourners.
How will Modi deal with Imran?
Why a future war with Pakistan is certain
'Hugging the Pakistani army chief is anti-national'
If Pak escalates, it'll lose more than India