More than 280 Iraqis have been killed and 400 wounded this week in the U.S. Marines' siege of insurgents in this city west of Baghdad (search), the director of Fallujah's (search) hospital said Thursday.

Taher Al-Issawi told The Associated Press that the toll was likely higher.

"We also know of dead and wounded in various places buried under rubble, but we cannot reach them," because of fighting, he said.

The U.S. assault on Fallujah began early Monday, when Marines surrounded the city of 200,000 people. Since then, U.S. forces have been waging heavy street battles, using warplanes and tanks against Sunni (search) insurgents dug in heavily populated neighborhoods.

At least three Marines are known to have been killed since the operation began, but commanders have not given an official toll.