An al-Qaida-related group in Iraq said Tuesday that the country has become "a university of terrorism" in an audio recording posted on an internet website.

Abu Omar al-Baghdadi, head of the self-styled Islamic State in Iraq, an umbrella group for eight other militant factions, including al-Qaida in Iraq, said fighters belonging to his group have used the war in Iraq, to achieve high levels of training.

"From the military point of view, one of the (enemy) devils was right in saying that if Afghanistan was a school of terror, then Iraq is a university of terrorism," al-Baghdadi said in the recording.

He said the largest batch of soldiers for the Islamic Jihad (Holy War) were graduating and they have the highest level of competence in the world.

Al-Baghdadi, who spoke to mark the fourth anniversary of the U.S.-led invasion of Iraq, said that his group was increasingly confident of success.

"The fear of the American marines has disappeared from the hearts of the people of the world, as the mujahideen have become thousands from the few they were after the fall of the infidel Baath regime," he said.

Al-Baghdadi also urged Iraqi insurgent groups to maintain their unity, warning that the enemies wanted to cause splits in their ranks.

Rifts are growing between al-Baghdadi's militant group and other Sunni insurgent groups that accused al-Qaida of imposing control over them.

In the recording, he said he strongly opposed any fighting between insurgent groups and he would take necessary measures to percent bloodshed.

Editor: Yan