The Prime Minister said what was more painful was the fact that this "senseless act of violence" should be targeted at a religious place.
An anguished Punjab Chief Minister Parkash Singh Badal asked the Prime Minister to take up with the Obama administration the issue of safety and security of Sikhs living in the US while the Sikh religious leadership said the attack by a lone white gunman was a security lapse on the part of US Government.
Condemning the attack, External Affairs Minister S M Krishna said it does not fit into the proclaimed policies of the US.
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.
The Sikh community in Jammu staged a protest and sought adequate security for their members and religious institutions in the US.
Reaching out to the Sikh community, US Ambassador to India Nancy Powell offered her prayers at Gurudwara Bangla Sahib in Delhi and said the incident will be probed thoroughly.
"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," Prime Minister Singh said in a statement.
Later talking to reporters, Singh said he was "enormously" saddened by the incident and hoped the "American authorities will investigate who were behind this dastardly attack".
In a letter to the Prime Minister, Chief Minister Badal said "there is a growing feeling in the minds of Punjabis in general and Sikhs in particular that the Union government must get more actively and vigorously involved in getting the US administration address the issue of safety in right earnest."
The US Embassy in a statement in Delhi said any incident like the attack on a Gurudwara one is tragic, especially when it happens in a place of worship.
