US MARINES backed by tanks and aircraft seized the heart of the holy Iraqi city of Najaf yesterday in a major assault on Shi'ite rebels, but they kept out of a site sacred to millions of Shi'ites around the world.

Explosions and gunfire echoed across the holy city of Najaf today as the US military and Iraqi forces launched a full-scale assault to crush a weeklong uprising by militiamen loyal to radical Shiite cleric Muqtada al-Sadr.