Abu Musab al-Zarqawi has been identified as an al-Qaida-linked operative and a lead suspect in many of the most ruthless and brutal acts of terror in Iraq this year. The 37-year-old Jordanian rose from a petty criminal to the top of the United States' most wanted terrorists list.

Abu Musab al-Zarqawi grew up in the Jordanian town of Zarqa from which he eventually took his name. Fellow Jordanian and director of the Jerusalem Center for Political Studies Uraib El Rantawi, says al-Zarqawi was an unremarkable petty criminal in his early years.

"Abu Musab al-Zarqawi was an ordinary guy. He used to live in the city of Zarqa. He has not been a politician. He was not interested in ideologies or religion even," he noted. "He has a record as a man who committed many violations of the law here, even many crimes, and he was arrested many times." It was in Jordanian jails that al-Zarqawi, whose real name is Ahmad Fadel al-Khalayleh, met several leading Islamic fundamentalist thinkers, and began to embrace their ideas. In the 1980s, when he was about 20-years- old, he went to fight in Afghanistan against Soviet forces.

After the Soviets were defeated, al-Zarqawi went back to Jordan and was rounded up along with other veterans of Afghanistan and accused of conspiring to overthrow the monarchy and establish an Islamic state. On his release four years later, he fled the country, and was sentenced to death in absentia for plotting attacks on American and Israeli targets.

His relatives in Jordan say they lost all contact with him long ago.

Reached at his home in Zarqa, a cousin of al-Zarqawi's who asked not to be named, said that al-Zarqawi had left 20 years ago, and that his relatives knew nothing about him afterwards.

Around 2000, al-Zarqawi traveled to Pakistan and then Afghanistan, where he renewed contacts with Osama bin Laden, organized training camps and recruited followers of his own. Two years later, he was accused of planning the assassination of U.S. diplomat Laurence Foley in Jordan, and in 2003, was linked to bombings in Casablanca and Istanbul.

In Iraq, his group, Tawhid wal Jihad (Unity and Holy War), has been blamed for the videotaped execution of American hostage Nicholas Berg, the killing of a Bulgarian truck driver and, most recently, of a Turkish worker. He is also seen as the brain behind the assassination of Ayatollah Muhammad Baqir al-Hakim and of at least 50 other Shia worshippers in Najaf, the attack on the U.N. compound last August and the recent coordinated attacks on Iraqi churches.

Last week, the United States raised the reward for the capture of the 37-year-old al-Zarqawi to $25 million.

In February, coalition officials in Iraq released a letter they said was written by al-Zarqawi, which outlined a strategy of destabilizing Iraq by provoking sectarian conflict. In the letter, he claimed responsibility for more than two dozen terrorist attacks.

Some analysts have expressed doubts that the poorly educated al-Zarqawi could have composed a letter in such formal Arabic, but Mr. El-Rantawi says the seasoned terrorist had plenty of time to educate himself.

"I don't think Zarqawi [is] that stupid, small criminal anymore. In the jail here in Jordan, he met one of the most important thinkers of al-Qaida, Abu Hamid El Magdisi. And he spent many months with this man, and I think he took a lot from this man," he said. "Those people [like al-Zarqawi], they don't attend university or schools to learn. They have their own sheikhs, they have their own people who teach them."

According to Muhamad Salah, a political analyst at the London-based Al Hayat newspaper, it is difficult to know anything for certain about al-Zarqawi's current activities in Iraq.

Al-Zarqawi could have already been killed or be hiding somewhere, says Mr. Salah. But his group has become the most famous and ferocious one in Iraq, and has used its experience in Afghanistan to turn Iraq into a new battlefront.