Washington - The United States condemned the terrorist attack on a bus in Russia's North Ossetia republic on Thursday that left 11 people dead.

"The United States condemns the heinous act of terrorism that took place today," State Department deputy spokesman Robert Wood said.

An explosion hit a crowded minibus in the populous city of Vladikavkaz as as it stopped for exiting passengers at the entrance to a movie theatre and market. Regional authorities said a preliminary investigation pointed to terrorism, but the source of the attack was unclear.

"We express our condolences to the families of the victims and the government of Russia for the loss of life and injuries that resulted from this terrible act," Wood said. "There can be no justification for such terrorism."

Vladikavkaz, the regional capital, was the target of multiple terrorist attacks by Islamist militants during Russia's war in neighboring Chechnya.

Tensions in the volatile region have increased amid the conflict across the border in Georgia that erupted in August over the separatist region of South Ossetia. Russia sent thousands of troops into South Ossetia after a Georgian military assault to retaliate for separatist attacks. (dpa)