BAGHDAD, Iraq - Iraqi security forces have arrested the "most lethal" top lieutenant of al-Qaida's leader in Iraq - a man allegedly behind 75 percent of the car bombings in Baghdad since the U.S.-led invasion, the prime minister's office said today.

Sami Mohammed Ali Said al-Jaaf, also known as Abu Omar al-Kurdi, was arrested during a Jan. 15 raid in Baghdad, a government statement said today. Two other militants linked to Jordanian-born Abu Musab al-Zarqawi's terror group also have been arrested, authorities announced today.

Al-Jaaf was "the most lethal of Abu Musab al-Zarqawi's lieutenants," the statement said.

Jordanian-born al-Zarqawi heads al-Qaida in Iraq, the terror network's local affiliate. The group is behind many of the car bombings, beheadings, assassinations and other attacks driving the insurgency in Iraq.

Al-Jaaf was responsible for 32 car bombing attacks that killed hundreds of Iraqis, the statement said.

"Abu Omar al-Kurdi claims responsibility for some of the most ruthless attacks on Iraqi police forces and police stations," said Thaer al-Naqib, spokesman for interim Prime Minister Ayad Allawi.

The statement said al-Jaaf "confessed to building approximately 75 percent of the car bombs used in attacks in Baghdad since March 2003," al-Naqib said.

Authorities also announced today that Iraqi security forces had arrested a man described as the chief of al-Zarqawi's propaganda operations.

And in the northern city of Mosul, Iraqi forces seized one of al-Zarqawi's weapons suppliers.