Thousands of U.S. troops have launched a major attack on the Iraqi city of Najaf, one of the holiest cities in the Muslim world. Shortly after dawn, U.S. tanks moved into the city center to block off roads to the holy Imam Ali Shrine, where the Prophet Muhammad’s son-in-law, Ali, is buried.

Helicopter gunships flew overhead. Warplanes bombed portions of the massive Shiite cemetary where some backers of cleric Moqtada Al Sadr are stationed. Thick black smoke poured into the sky. Thousands of residents in Najaf have fled the city to escape the fighting which has raged on for the past week. Agence France Press is reporting the downtown area looks like a ghost city.

The New York Times estimates the U.S. has tripled the number of troops around Najaf to about 5,000. A U.S military spokesperson told the press “Major operations to destroy the militia have begun.” Sadr told his followers “I hope that you keep fighting even if you see me detained or martyred.”

In Basra and Baghdad, thousands of Shiite Iraqis took to the streets to protest the U.S. attack on Najaf. Shiites around the world are warning the U.S. against directly attacking the holy shrine. One Shiite cleric in Los Angeles said “Any attack on that city will destroy America’s future in Iraq completely. It will completely discredit America and make it the new tyrant in the eyes of Shias worldwide.”

U.S. forces have also attacked the Shiite city of Kut reportedly killing 72 people over the past 24 hours. Agence France Press is reporting that across Iraq 165 people have been killed and nearly 600 wounded over the past 24 hours.