With a $10 million bounty on his head, Abu Musab al-Zarqawi is one of the most hotly sought Islamic extremist leaders with links to al-Qaida.
The Jordanian is suspected of planning some of the worst terror bombings in Iraq and is believed to have written a captured document sent to al-Qaida commanders outlining a campaign to foment civil war between Iraq's Sunni and Shiite Muslims.
He was linked to deadly bombings last year in Turkey and Morocco and is accused of orchestrating the 2002 assassination of a U.S. diplomat in Jordan. And Britain tied him to a foiled ricin poisoning plot.
In Iraq, Col. Ralph Baker of the 1st Armored Division said this week's bombings resembled "the operating technique" of al-Qaida or Ansar al-Islam, a radical Muslim group based in Iraq's Kurdish region that is affiliated with Osama bin Laden's network. Officials in Washington, Jordan and other countries have said al-Zarqawi has strong ties to Ansar.
After the U.S.-led war that ousted the Taliban regime in Afghanistan two years ago, Washington described al-Zarqawi as one of eight al-Qaida operations chiefs and listed him among about two dozen of the most-wanted fugitives.
Last year, Secretary of State Colin Powell used al-Zarqawi as an example of al-Qaida ties to Saddam's regime, saying al-Zarqawi received hospital treatment in Baghdad after fleeing Afghanistan. Intelligence sources said he apparently was fitted with an artificial leg.
U.S. intelligence officials also said then that al-Zarqawi considered himself and his followers to be operating independently of al-Qaida's chain of command. But they said he relied on al-Qaida for money and logistical support.
Al-Zarqawi, 37, was born Ahmad Fadeel Nazzal al-Khalayleh, but uses a nom de guerre derived in part from the name of his hometown in Jordan, Zarqa. Now believed to be hiding in Iraq, he has been involved with Islamic militant groups since going to Afghanistan in the late 1980s to help fight the occupying Soviet army.
According to his family, he returned to Zarqa, an industrial town 17 miles from the Jordanian capital, Amman, in 1992. The family, which belongs to the Bedouin tribe Bani Hassan, says he married but couldn't find work.
His mother, Um Sayel, last year described her youngest son as a modest man and devout Muslim and said he was wrongly being accused of terrorist activities. "My son is a good man, an ordinary man, a victim of injustice," she said.
Um Sayel, who uses her eldest son's name for identification, wouldn't talk about al-Zarqawi's 1992-97 stint in prison. Jordanian security officials say he was jailed for working with groups that wanted to overthrow the monarchy and set up an Islamic state and also plotted to attack foreigners in Jordan.
Al-Zarqawi fled Jordan in 1999, shortly before authorities announced they had foiled a gas attack on American and Israeli tourists during millennium festivities and charged him with planning the assault. Jordanian officials say he went to Afghanistan, where they say he showed a talent for making poison gas and developed close contacts with bin Laden.
He reportedly left Afghanistan as the Taliban regime collapsed two years ago, apparently having been wounded during the U.S. bombing or in fighting with Washington's Afghan allies. U.S. authorities say he stayed in Iran for a time, then spent two months in Baghad receiving medical care.
Intelligence officials in several countries say al-Zarqawi has been on the move ever since, forging new terrorist cells and planning attacks.
A little over a year ago, Jordanian authorities named al-Zarqawi as the mastermind behind the October 2002 murder of Laurence Foley, a 60-year-old administrator of U.S. aid programs in Jordan.
In a German court last year, Shadi Abdellah, a Palestinian on trial for allegedly plotting to attack Berlin's Jewish Museum and a Jewish-owned disco, testified he was working for al-Zarqawi. He said they met in Afghanistan.
German authorities have reportedly said they believe al-Zarqawi was appointed by al-Qaida's leadership to arrange attacks in Europe.
Moroccan government sources said a group blamed for bombings last May that killed 45 people in Casablanca got its orders from al-Zarqawi. In Turkey, officials said he was believed to have played a role in bombings that killed 63 at two synagogues, the British consulate and a British bank in Istanbul in November.