'Caliph of All Muslims': Who is Abu Bakr al-Baghdadi?

The jihadist militants, ISIS on Sunday declared that they are building a "caliphate" state and proclaimed their leader, Abu Bakr al-Baghdadi, as the caliph of the area saying he would be the "leader for Muslims everywhere".

The group renamed itself as "Islamic State" with the announcement and installed a new face as the extremist group's leader, leaving the United States and the rest of the world worried about the rise of a new threat to international peace.

The declared leader of the 'caliphate' is known to be a shadowy jihadist, fighting in Iraq and Syria, increasingly being seen as more powerful than the current Al-Qaeda's chief Ayman al-Zawahiri .

The leader was on Sunday elevated to the coveted position, by the Islamic State of Iraq and the Levant (ISIL) militant group recreating a history of the caliphate system that the world thought had died 100 years ago with the fall of the Ottoman Empire.

"The Shura (council) of the Islamic State met and discussed this issue (of the caliphate)...The Islamic State decided to establish an Islamic caliphate and to designate a caliph for the state of the Muslims," ISIL spokesman Abu Mohammad al-Adnani said in an audio recording distributed via websites and Twitter.

"The jihadist cleric Baghdadi was designated the caliph of the Muslims," he added.

Washington believes Baghdadi was born in Samarra in 1971 and joined the growing insurgency group shortly after US led an invasion of Iraq in 2003. The leader was, at one point, put into an American military prison in the country.

Though reluctant, America is weighing options on whether or not to be fully drawn into the current war in Iraq, as it sees a danger in the growth of a new terrorist outfit.

The leader of the group had reportedly warned the United States of a potential attack when he was released from the prison in Iraq. The Daily Beast reported citing Army Col Kenneth King, the then commanding officer of Camp Bucca, that Badhdadi had said "I'll see you guys in New York" when he walked away from the US detention camp in 2009.

In October 2005, American forces had said they believed they had killed "Abu Dua", one of Baghdadi's known aliases, but the news happened to be incorrect as he started leading the group, which was then known as the Islamic State of Iraq (ISI) in May 2010 after two of its chiefs were killed in a US ambush.

Baghdadi was kept in the US cell for four years, but the United States intelligence hadn't been able to weigh the scale of danger he would pose to the world peace, especially the Unites States. He wasn't even assigned to Compound 14 of the detention camp, which was reserved for the most virulently extremist Sunnis, reports have said.

In October 2011, the US Treasury declared him a "terrorist". Earlier this year, Iraq released a picture of a bald-headed, bearded man in a suit and tie, which they said was Baghdadi.

Touted within ISIL group as a battlefield commander and tactician, the leader is believed to be currently inside Iraq, although officials are not sure about his exact whereabouts.