Congress leader and former Defence Minister A.K. Antony said the attack that left 17 soldiers dead was "a serious security lapse".
Antony told media persons here that the Kashmir issue was "drifting and reaching dangerous propositions".
"This incident comes close on the heels of what happened in Pathankot. At both these places, the militants managed to enter military camps and this is a huge security lapse," he said.
Congress President Sonia Gandhi described the terror strike as a "cowardly attack as a deplorable affront on our national conscience".
She hoped that "the perpetrators of this dastardly act as also the forces behind them will be severely dealt with and brought to book".
In a tweet, former Home Minister P. Chidambaram said: "Government must mobilise all resources, manpower and material, to strengthen border defence to prevent infiltration of terrorists."
Rashtriya Janata Dal (RJD) chief Lalu Prasad went on to take a dig at Prime Minister Narendra Modi and said: "Soldiers are dying due to the failure and negligence of Modi; where is his 56-inch chest now."
He said Jammu and Kashmir is an integral part of India but the situation there is going out of control, thanks to "only big talk and no action" on the ground.
The Central Committee of the Communist Party of India (Marxist) also condemned the killing of 17 Indian army personnel and maintained that Pakistan "must stop aiding and abetting the extremist forces".
"Despite the deployment of a large number of security personnel, the government has failed to stop the continuing infiltration of militants," the party said in a statement.
The CPI-M, which began its two-day Central Committee meet on Sunday in New Delhi, maintained that "for a longstanding solution of the Kashmir problem, political dialogue with all stakeholders as advocated by the all-Party delegation should be initiated without any further delay".
In a tweet, Congress Vice President Rahul Gandhi "condemned" the militant attack and said: "My heartfelt condolences to the families of the bravehearts martyred in the attack."
