In a statement this week, a group calling itself Hamas in Iraq -- a breakaway from the Sunni insurgent network called the 1920 Revolution Brigades -- lashed out at al-Qaida in Iraq, accusing them of slaughtering ordinary Iraqis.

"Every day (the inhabitants of Fallujah, when it was under al-Qaida control) witnessed heads or headless bodies lying in their streets. … None of them were Americans. Rather, they were all local people from the area -- people who, at one point, had supported the al-Qaida network until they themselves had become disposable."

The group said it had previously kept its criticisms and disagreements with al-Qaida private, "so that the infidels and our enemies would not rejoice over our differences."

It said it had been forced to speak out now "due to recent events and the behavior of certain individuals."

Analyst Evan Kohlman wrote Thursday on the Counter-Terrorism Blog that the recent events are likely a series of statements from the Islamic State of Iraq -- an umbrella for al-Qaida and other jihadi groups -- attacking Hamas in Iraq, the 1920 Brigades and other organizations.

Over the past several weeks, Kohlman wrote, the Islamic State of Iraq has issued a series of increasingly outspoken "communiques blasting fellow Sunni insurgents for 'deviating' from the path of legitimate jihad and working directly with U.S. military forces in Iraq."