A statement posted on the Internet in the name of Osama bin Laden's Al Qaida network has claimed responsibility for an attack on the UN headquarters in Baghdad last week which killed 23 people, including the head of mission.

It was posted in Arabic late on Sunday on the discussion Web site www.myislah.org and dated August 19, the day of the attack on the UN headquarters.

The statement's authenticity could not be verified. On Thursday, an Arabic television channel reported a previously unknown Iraqi group had claimed responsibility for the attack.

Written in heavily symbolic and oblique language, the latest statement was signed by Brigades of Abu Hafs Al Masri and followed by the words Al Qaida in parentheses. It referred to a previous warning issued on August 15 in which it said it would "exhaust and confuse" America and its "henchmen".

"We meant that we would carry out such a lethal and surprising attack that the enemy will not know where, when and how we will strike."