Washington, August 1 (IANS): Condemning the vandalism at a Sikh gurdwara in Riverside, California as "reprehensible", an influential US lawmaker has urged officials to investigate the incident as a possible hate crime and send a powerful message against such attacks.

"I am deeply troubled by the events that took place on Tuesday at the Sikh Gurdwara in Riverside," said House member Joe Crowley, vice chair of the House Democratic caucus referring to some unidentified individuals spray painting the word "terrist!" on the gurdwara walls.

"Enough is enough. The pattern of violence against the Sikh-American community is reprehensible and we must send a powerful message to people responsible that we will not tolerate this kind of attack against any community - whether it is in New York, California or anywhere else," he said.

"As we approach the anniversary of the terrible tragedy at Oak Creek, I urge officials to investigate the incident as a possible hate crime," Crowley added.

Six worshippers were shot dead at a Sikh gurdwara at Oak Creek Wisconsin by a White supremacist on Aug 5 last year sending shock waves through an estimated half a million strong Sikh community.

In recent years, Sikh-Americans and their religious institutions have been threatened or attacked in highly-publicized incidents in Wisconsin, New York, Michigan, Virginia and California, Crowley noted.

Advocacy groups believe it is likely that many other incidents have occurred but went unreported.

In April 2012, Crowley led a letter signed by 93 members of Congress urging the FBI and Department of Justice to begin tracking and documenting hate crimes committed against Sikh-Americans.

Meanwhile, North American Punjabi Association (NAPA) has also expressed its concern about the increasing number of attacks on Sikhs and vandalism at Sikh gurdwaras.

Asking the FBI and US Justice Department to investigate the Riverside incident as a hate crime, NAPA executive director Satnam Singh Chahal said due to such incidents Sikhs in the US are living under the shadow of fear and insecurity.