The involvement of Jaish-e-Mohammad in Thursday's terrorist attack in Jammu and Kashmir has raised serious questions about the role of the Pakistani spy agency, ISI, in it, American experts on South Asia have said. The Pakistan-based JeM has claimed responsibility for the attack that left at least 37 personnel dead and many critically wounded. The experts said the terror strike shows the United States has failed to persuade Pakistan to act against Jaish-e-Mohammad and other terrorist groups. "The self-proclaimed involvement of JeM in the attack raises serious questions about the role of the ISI in supporting the masterminds of this operation," Bruce Riedel, a former CIA analyst, told PTI. Also read|\u00a0Pulwama attack LIVE Updates: Rajnath Singh to visit Srinagar, mobile internet services suspended in Jammu The terrorist attack, which has direct footprints inside Pakistan, poses the first major challenges to Pakistan Prime Minister Imran Khan, said Riedel, who is now a scholar at the Brookings Institute think-tank. "This will be a real challenge for Imran Khan, the first serious challenge of his administration," he said. Anish Goel, a former National Security Council official in the previous Obama administration, said the horrific attack highlights just how actively Pakistan-based terrorist groups still operate in Kashmir. \u201cBy claiming such quick credit for the attack, Jaish-e-Mohammed is clearly indicating that they will continue to cause trouble in the region and stoke tensions between Pakistan and India,\u201d he said. \u201cIn the wake of this attack, there will likely be increased pressure on Prime Minister (Narendra) Modi to take action against all militant groups still active in Kashmir," said Goel.