A doctor and five labourers were killed when terrorists struck a tunnel-construction site on the Srinagar-Leh national highway in Jammu and Kashmir's Ganderbal district on Sunday, officials said.

The unidentified terrorists carried out the attack when the labourers and other staff working on the tunnel project at Gund in Ganderbal had returned to their camp late in the evening, the officials said.

They said the terrorists -- believed to be at least two -- opened indiscriminate fire on the group of labourers that included both locals and non-locals.

While two labourers died on the spot, three others and the doctor succumbed to their injuries subsequently, the officials said, adding that five people are undergoing treatment for injuries.

Security forces have cordoned off the area and launched a search operation to track down the attackers, they said.

Top security officials, including Inspector General of Police (IGP), Kashmir, V K Birdi, have reached the spot to assess the situation.

Meanwhile, Chief Minister Omar Abdullah said the number of casualties in the attack may go up.

"The casualty figure from the Gagangir attack is not final as there are a number of injured labourers, both local and non-local. Praying that the injured make a full recovery as the more seriously injured are being referred to SKIMS, Srinagar," he said in a post on X.

Abdullah condemned the attack, which came barely four days after he was sworn in as the chief minister of the Union Territory.

"Very sad news of a dastardly and cowardly attack on non-local labourers at Gagangir in Sonamarg region. These people were working on a key infrastructure project in the area. 2 have been killed and 2-3 more have been injured in this militant attack. I strongly condemn this attack on unarmed innocent people and send my condolences to their loved ones," he said in another post on the microblogging platform.

Lieutenant Governor Manoj Sinha strongly condemned the heinous terror attack on civilians. "I assure the people that those behind this despicable act will not go unpunished. We have given full freedom to J&K Police, Army and security forces," Sinha said in a post on X.

Former Jammu and Kashmir chief minister and People's Democratic Party (PDP) president Mehbooba Mufti also condemned the attack.

"Unequivocally condemn this senseless act of violence against two labourers in Ganderbal. Deepest condolences to their families," she said in a post on X before the officials revised the death toll in the incident.

In a post on X, People's Conference leader Sajad Gani Lone said: "Strongly condemn the dastardly act of terror wherein two persons have lost their lives in Sonamarg. This is an insane act of madness. My thoughts with these two families. May the perpetrators be brought to justice." Jammu and Kashmir Pradesh Congress Committee (JKPCC) president Tariq Hameed Karra expressed grave concern over the attack and said such incidents will vitiate the atmosphere in the Union Territory. He urged the government to take immediate measures to prevent such brutal attacks on innocent labourers.

On Friday, the bullet-riddled body of a labourer from Bihar was found in Shopian district, officials said.