American officials are questioning Iraq's former Deputy Prime Minister, Tariq Aziz, following his arrest, the US military says.
Tariq Aziz was 43rd on the Americans' "most wanted" list
They are keen to discover if Mr Aziz - a high-profile figure in the ousted government - has information on the whereabouts of former President Saddam Hussein and any weapons of mass destruction.
Mr Aziz, 67, is reported to have surrendered to US-led coalition forces in the Iraqi capital Baghdad after several days of negotiations.
He served as Iraqi foreign minister for many years, and was internationally the most recognisable face of the Iraqi Government after President Saddam Hussein.
A former Iraqi exile who has declared himself governor of Baghdad, Mohammed Mohsen Al-Zubaidi, told the BBC that he gave the Americans the information that led them to arrest Mr Aziz and his family.
Born in 1936, near Mosul, northern Iraq
Studied English literature and became a journalist
The most senior Christian in the toppled regime
Enlisted US support for war on Iran
Met US President Ronald Reagan at the White House in 1984
Was Saddam Hussein's deputy for more than a decade
The BBC's Clare Marshall in Baghdad says Mr Aziz is a Christian and not a member of Saddam's Tikriti clan, and so was outside the regime's innermost circles.
However, she adds that his high-profile international role means that he is a key figure for the coalition to have in custody.
American forces have also detained a former Iraqi intelligence chief, Farouk Hijazi, near Iraq's border with Syria.
Mr Hijazi also served as Iraqi ambassador to Turkey and Tunisia, but - unlike Mr Aziz - he is not among the 55 leading Iraqi officials the Americans have been seeking.
Mr Aziz is the 12th person on that list to have been caught, according to the US. As a member of Iraq's Revolutionary Command Council, he was wanted for war crimes against Kuwait, Iran and his own people.
In other developments:
- Coalition forces have killed "several" Iraqi paramilitaries and destroyed their vehicles after coming under attack near the north-western city of Mosul, the US military says
- The first post-war international meeting of Iraqi political groups begins in the Spanish capital, Madrid
- Thousands of Shia Muslims in the Iraqi holy city of Karbala demonstrate against the American presence in the country following Friday prayers
- US Defence Secretary Donald Rumsfeld says a "vocal minority" of pro-Iranian Shias will not be allowed to seize power in Iraq
- UK Foreign Secretary Jack Straw says UN weapons inspectors
should be allowed to resume their work in tracking down any weapons of mass destruction in Iraq
- The UN refugee agency says it is planning to help up to half a million Iraqi refugees return home from exile.
The US Government has welcomed the capture of Mr Aziz.
White House spokesman Ari Fleischer said the rounding up former regime officials would help build a "stronger
future" for Iraq.
A British Member of Parliament, Ann Clwyd, said it was essential that Mr Aziz stand trial for war crimes and genocide.
IRAQI LEADERS IN CUSTODY (AS RANKED BY US FORCES)
10. Muzahim Sa'b Hassan al-Tikriti
18. Muhammad Hazmaq al-Zubaidi
21. Zuhayr Talib Abd al-Sattar al-Naqib
24. Samir al-Aziz al-Najem
40. Jamal Mustafa Abdallah Sultan al-Tikriti
43. Tariq Aziz
45. Hikmat al-Azzawi
48. Muhammad Mahdi al-Salih
51. Watban Ibrahim al-Tikriti
52. Barzan Ibrahim Hasan al-Tikriti
54. Humam Abd al-Khaliq Abd al-Ghafur
55. Amir Hamudi Hasan al-Sadi
The US identified key government figures it wanted captured - or dead - before it launched the war on Iraq.
Some may be put before war crimes tribunals, but correspondents say that in the short term, coalition leaders will be more anxious to get information from them about how the regime functioned and where weapons might be stored.
There had been fears that regime leaders would flee Iraq, perhaps into Syria.
But arrests continue to be made in Iraq, and officials such as UK Foreign Secretary Jack Straw say they believe Saddam Hussein is still inside his country.
Mr Aziz was often sent abroad to argue Iraq's case.
He first came to world prominence with his fluent English, trademark black-rimmed glasses and Cuban cigars during his time as foreign minister during the first Gulf War in 1991.
Shortly before the war began last month, he met Pope John Paul II to call for peace.
He last appeared in public on 19 March, when he held a news
conference in Baghdad to quash rumours that he had fled the Iraqi