US Secretary of State Hillary Clinton called her Indian counterpart Monday after a man attacked a Sikh temple in Wisconsin killing six people before being shot dead himself, a US official said.

Clinton, who is on a visit to South Africa, spoke with Indian Foreign Minister S.M. Krishna a day after Sunday's attack.

"Our hearts go out to the victims, the families and Sikh community," said State Department acting deputy spokesman Patrick Ventrell.

"This is a tragic incident, especially since it happened in a place of worship. Religious freedom and religious tolerance are fundamental pillars of US society."

According to the Press Trust of India news agency, Krishna conveyed India's concern that such a "heinous crime" had occurred in a place of worship and said US President Barack Obama needed to address fears of similar attacks in the future.

"An assurance to the Indian community has to come out from the Obama administration that their interests are going to be safe," Krishna said.