A senior member of Al Qaeda in Iraq was killed during an operation in Baghdad this week carrying letters for Usama bin Laden and the new leader of the terror group's Iraqi offshoot, an Interior Ministry official said Thursday.

In a separate announcement, the top U.S. military spokesman in Iraq said U.S. forces had arrested a senior Al Qaeda terrorist and personal associate of the group's new leader, Abu Ayyoub al-Masri.

Abu Jaafar al-Liby, who was either the second or third most important figure in Al Qaeda in Iraq, was killed by police during an operation three days ago, Interior Ministry spokesman Brig. Abdul-Karim Khalaf told The Associated Press.

Four other insurgents were killed and two were arrested in the raid, Khalaf said.

Al-Liby had been in charge of the Baghdad sector of Al Qaeda in Iraq, Khalaf said. He said two letters were found on his body -- one for bin Laden and the other for al-Masri, who took over Al Qaeda in Iraq from Abu Musab al-Zarqawi after he was killed in a U.S. airstrike north of Baghdad on June 7. Both letters pledged loyalty and promised more attacks.

It was not immediately known if the killing announced by Khalaf was related to the operations that led to the arrest of the unidentified Al Qaeda terror suspect described by Maj. Gen. William B. Caldwell said, the top U.S. military spokesman.

The suspect, who was arrested Tuesday, was the leader of assassination, kidnapping and bomb-making cells in Baghdad, Caldwell said, adding he was a "personal associate" of al-Masri.

"It is known he directly participated in numerous terrorist acts, including kidnappings and executions, terrorist acts and others contributing to sectarian violence throughout the city," he said of the suspect.

Caldwell said the man also played a key role in Al Qaeda's activities in Fallujah before it was attacked by U.S. troops in November 2004.

Caldwell said U.S. and Iraqi forces had carried out 25 raids around Baghdad on Tuesday, resulting in the arrest of more than 70 suspected terrorists.