Gunmen attacked the American Center Library in India's eastern city, Kolkata, also known as Calcutta, early Tuesday. Reports from the scene say four guards were killed and a number of bystanders were wounded in the attack.

Witnesses say two men on a motorcycle sprayed the entrance of the American Center with gunfire, just past dawn on Tuesday.

The four-story building is in the center of the city. It houses a large library, a cultural center and the offices of the U.S. Consulate's public affairs section. No one was inside the building when the attack occurred. The U.S. Consulate, which issues visas, is at a different part of the city.

There has been no claim of responsibility for the attack. It took place as Robert Mueller, the director of the U.S. Federal Bureau of Investigation, arrived in New Delhi for consultations with Indian officials on counter terrorism cooperation.

Authorities say many of the wounded were gravely injured anfd the death count could rise.