This from the USAToday website, from a story posted last Friday:

"Much of the world reacted in horror to Berg's death and the grisly video that recorded it. U.S. intelligence officials have concluded that terrorist leader Abu Musab al-Zarqawi, who has a $10 million price on his head by the U.S. government, was the person shown decapitating Berg."

This from Japan Today, regarding the arrests:

"It was understood that none of the four included al-Qaida linked Jordanian extremist Abu Mussab al-Zarqawi, who U.S. authorities believe carried out the killing of the 26-year-old along with other atrocities in Iraq.

However, Brig Gen Mark Kimmitt, deputy director of operations, said: "We have no information from the coalition that any arrests were made today." (Wire reports)"

This from the DoD website, from a transcript of a press conference today:

"Q    Stephanie Halasz, CNN. One question regarding Nicholas Berg. We're hearing that there are reports that four arrests were made regarding the killing of Berg. Can you tell us anything about that?



            GEN. KIMMITT: We have no information on the coalition that any arrests were made today."


I haven't found any reference to al-Zarqawi being killed.