Police in India are searching for unidentified shooters after a firing at a military base in the border state of Punjab killed four soldiers.

The soldiers were shot at the military station in Bathinda on Wednesday.

Police say the incident, which took place in the base's barracks, was "not a terror attack".

No arrests have been made yet, but the army said it had found an assault rifle believed to have been used in the firing.

Ajay Gandhi, a senior police officer from Bathinda who is heading the investigation, told Reuters that a police complaint has been filed based on a statement of an army personnel, which refers to the involvement of "two unknown people" in the attack.

A search operation was underway all of Wednesday as authorities sealed the military station, set up barricades and deployed drones to locate the attackers.

Located about 280km (175 miles) from capital Delhi and 100km east of the border with Pakistan, the Bathinda Military Station is one of the largest army bases in India.

The base serves as a vital operational and logistics base for Indian army units in Punjab and parts of the neighbouring Rajasthan state.

The army said the attack occurred 4:35am (2305 GMT Tuesday) on Wednesday when the soldiers were sleeping in their rooms.

The four soldiers succumbed to gunshot injuries sustained during the firing.

A police investigation was opened based on the statement given by Major Ashutosh Shukla, who said he had caught a glimpse of the shooters.

In his statement, Major Shukla said he rushed to the spot after a soldier informed him that there had been a firing in the officers' mess.

He said he saw two men "of medium height and good build" armed with a rifle and an axe fleeing from the site of the attack. The men wore kurta-pyjamas and had their faces covered with a cloth, he said in the complaint.

At the barracks, Major Shukla said he saw the bodies of two soldiers in one room and two more bodies in the adjacent room. All four of them had bullet marks, he said.

"We also found that a large number cartridges of the Insas rifle scattered in the rooms, which belongs to an open-ended Insas rifle," he said in the complaint, adding that one such rifle had been reported missing from their unit two days previously.

On Wednesday evening, the army said it had recovered the missing rifle along with its magazine and that it would be subjected to a forensic analysis.

"The number of rounds (unused) in the weapon will only be available after forensic analysis. The joint investigation with Punjab police is in progress," it said.

The Punjab Police said that the incident was not a terrorist attack but a fratricidal incident.

On Wednesday, Punjab minister Anmol Gagan Maan told reporters that the firing was "a matter of an internal fight".

Police said the bodies of the four soldiers were sent to the Bathinda civil hospital for an autopsy.

Mr Gandhi from Bathinda police told Reuters that the search for the assailants was still underway.

"The attackers had only one rifle. The weapon carried by the other attacker is still being investigated," he added.

Meanwhile, the army on Thursday said that another soldier at the military station had died of a gunshot wound at around 4.30 pm on Wednesday.

However, it said the incident was not related to the shooting and "purportedly seemed to be of attempted suicide".

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