General John Abizaid said the coordinated bomb attacks that killed around 200 people at Shia Muslim shrines this week bore the hallmark of Abu Musab al-Zarqawi, a Jordanian accused of links to the al Qaeda network.
"He's somewhere in Iraq," Abizaid said in an interview on the public television program "The NewsHour with Jim Lehrer."
"We're looking for him hard and we've found quite a few of his operatives and we've taken out a couple of his senior operatives and we've uncovered an awful lot of the work that he's doing," said Abizaid, the head of US Central Command.
Iraqi and US officials accuse Zarqawi of waging a campaign to foment civil war in Iraq. U.S. forces have put a $10 million bounty on his head.
The attacks came durng a Shia
"I believe the threat that he presents to peace and stability in Iraq is one that should worry both the Iraqi authorities and American authorities," Abizaid said of Zarqawi.
In London, an Arabic-language newspaper has received a statement, purportedly from al-Qaida, denying the group was behind the attacks at the Shia pilgrinage sites.
The statement, a copy of which was obtained by Aljazeera.net on Thursday, blamed US "crusaders" for the attacks.
"We say to all Muslims: we had nothing to do with this act," said the statement.
It charged the attacks were "an American plot aimed at provoking sectarian conflict between Muslims in Iraq".
"Our aims are clear: we are striking the American crusaders and their allies. We are striking the Iraqi police who are being used by the US to strike the mujahidin in Iraq."
"We are striking the agents of the US in the Council of Infidels, the so-called Governing Council and people associated with it, whether they are Sunni or Shia," the statement read.
The president of the US-appointed Iraqi Governing Council on Thursday suggested the bombings in Iraq were occurring because US forces have failed to maintain security.
In London, an Arabic-language newspaper has received a statement, purportedly from al-Qaida, denying the group was behind the attacks at the Shia pilgrinage sites
Abizaid said that before the latest blasts, US authorities had indications there would be an attack and numerous precautions were taken. But he suggested it was impossible to completely secure Iraqis against such attacks.
"In a city of one million people like Kerbala, or five million like Baghdad, you can't be in all places at all times," Abizaid said. "It's also natural in that part of the world to blame what people view as the most important authority in the region and that currently is the United States of America."
Bin Ladin search
Commenting on the effort to catch al Qaida leader Usama bin Ladin, Abizaid denied reports that it was driven by election-
year pressure from the Bush administration.
"I think that we will make it very painful for al Qaida between now and the end of the year."
General John Abizaid
Head: US Central Command.
Bin Ladin, blamed for the Sept. 11, 2001, attacks on America, is believed to be hiding in Pakistan or Afghanistan.
Asked if he thought bin Ladin would be captured before the November election, Abizaid said he had no way of knowing, but added: "I think that we will make it very painful for al Qaida between now and the end of the year."