US authorities have said they are investigating reports that a gunman who killed six people at a Sikh temple in Wisconsin had white supremacist links.

Wade Michael Page, 40, who was gunned down by police during Sunday's attack near Milwaukee, reportedly performed in a far-right music group. President Barack Obama said on Monday "soul searching" was needed about how to reduce violence in the US.

The FBI is treating the attack as a possible domestic terrorism case. American Sikhs have reported being targeted since the 9/11 attacks, because they are mistaken for Muslims as a result of wearing turbans and beards.

Police chief John Edwards told a Monday morning news conference they were confident Page was the only shooter.

The gunman opened fire at the Sikh Temple of Wisconsin in Oak Creek as dozens of people were preparing for a service on Sunday morning. Five men and a woman aged between 39 and 84 died. Four people were found dead inside the building, and two outside....

....The gunman also fired at a police car and ignored orders to drop his weapon, before he was shot dead outside by police, said the authorities.

Page used a 9mm semi-automatic pistol, which was recovered at the scene and had been bought legally, authorities said.

A civil rights group, the Southern Poverty Law Center, has described Page as a "frustrated neo-Nazi".

>>>> A Joker and now a neo nazi... when are the gun laws in the USA going to get responsible, to which the nutters in the USA are screened out before they get the chance to buy thousands of rounds of ammunition online in one hit and kill people? Is it so against the 'constitution' that mentally unstable people are restricted from owning guns? Can't they just have one like in the old days???