"I am deeply shocked and saddened to learn of the shooting incident that has resulted in the loss of precious lives and injuries to devotees attending a prayer service at a gurudwara in Wisconsin, USA," he said in a statement here.
"We hope that the authorities will reach out to the grieving families and ensure conditions that such violent acts are not repeated in the future," Singh said.
The Prime Minister said what was more painful was the fact that this "senseless act of violence" should be targeted at a religious place.
"I send my deepest condolences to the families that have been bereaved in this incident. Our thoughts are with them in this moment of their grief."
Stating that India stands in solidarity with all the peace-loving Americans who have condemned this violence, he welcomed US President Barack Obama's statement on the tragic incident. Later talking to reporters, the Prime Minister said he was "enormously" saddened by the incident and hoped the "American authorities will investigate who were behind this dastardly attack".
"...I sincerely hope that the American authorities will do all that is necessary to investigate the case, provide relief and succour to the affected families," he said.
Six people were killed in the attack on the gurudwara during Sunday morning prayers in Wisconsin by at least one gunman who was also shot dead, police said.