A Web posting in the name of a militant group in Iraq (search) claimed Tuesday to have executed an Italian female journalist, but there was no way to determine the report's credibility.

The posting was signed by a different group than the one that had earlier claimed to have kidnapped Giuliana Sgrena (search). Both statements were posted on a Web site used as a clearing house for militants.

The Jihad Organization had earlier claimed responsibility for Friday's kidnapping of Sgrena, 56, but Tuesday's statement was signed by the Mujahedeen Brigade in Iraq (search).

"Your brothers in the Mujahedeen (holy fighters) Brigade have executed the Italian journalist Giuliana Sgrena after making sure that she has spied on the mujahedeen for the American Crusade troops," said the statement.

It said the killing was a message to the American government "that this would be the destiny of agents and spies." It was also warning to Italy against continuing with America in its war on Iraq and a message to the holy fighters to "carry on that path until the liberation of the last spot from Muslim land, and know that the occupation of Iraq is the beginning of the end of America, God willing."

On Monday, a Web posting in the name of the Jihad Organization pledged to release Sgrena in a few days because an investigation determined she was not a spy and after an appeal for her freedom by Sunni clerics.

Sgrena a reporter for the communist daily Il Manifesto, was kidnapped Friday by gunmen who blocked her car outside Baghdad University. An earlier posting by the Jihad Organization gave Italy 72 hours to withdraw its troops from Iraq.