text: US troops reach centre of Fallujah as 48 killed in Baquba and &lt;b&gt;...&lt;/b&gt; FALLUJAH: Iraqi Prime Minister Ayad Allawi on Tuesday imposed a night curfew in Baghdad as US troops with crack Iraqi soldiers surged into the heart of Fallujah in a hail of explosions and gunfire on the second day of the largest operation in Iraq since 