Iraqi intelligence chief Husain Ali Kamil declined to say whether Sabawi Ibrahim al-Hassan al-Tikriti had been expelled from Syria.
But he said the capture of the former president's half brother and former adviser resulted from arrests in the northern Iraqi city of Mosul and patrols by Iraqi forces on the Syrian border, particularly in al-Anbar province.
"This is not our problem if the Syrians put pressure on him or not. But he was crossing the border in and out of Iraq regularly and we spotted him three days from today," the intelligence chief said on Monday.
"We were very active in Hiyt and Rawa by the Syrian border for the last two months."
Al-Tikriti's arrest was announced on Sunday, but no further details were revealed.
Kamil accused him of funding anti-US fighters from Syria with millions of dollars from the Baath Party.
"He was crossing the border in and out of Iraq regularly and we spotted him three days from today"
Husain Ali Kamil, intelligence chief in Iraq's Interior Ministry
"It's a big success for us. He was the financier of the rebellion. He dispensed huge amounts of money for the Baath. He was involved directly in a number of attacks. The information they got from men arrested in Mosul was valuable in catching him."
Working from Syria
Kamil warned that the fighting would not stop any time soon and he pointed to the continued presence of Iraqi Baath leaders in Syria.
"I don't think it will put an end to the terrorism because there are other leaders from the Baath working in Syria."
Along with al-Tikriti, Iraqi and US officials have pointed to former Hussein aide and Baath party official Muhammad Yunus al-Ahmad as the other main leader working from Syria.Iraqi journalist Ziyad al-Samarrai told Aljazeera that there was little surprise or interest in the arrest.
Even though an Iraqi official said on Sunday "he's a big catch",
He said people received the news of the arrest of al-Tikriti - formerly the director of general security and Iraq's representative in Switzerland - calmly and without surprise, considering it quite ordinary.
Several months ago the interim government said al-Tikriti was one of at least two former Baath Party officials directing ongoing anti-US attacks from Syria.
"I don't think it will put and end to the terrorism because there are other leaders from the Baath working in Syria"
Al-Tikriti's brothers, Watban and Barzan, are already in custody at a US military-run facility on the outskirts of Baghdad and are due to be tried soon.
The arrest means only about 10 people on a Washington's most-wanted list, including Izzat Ibrahim al-Duri, remain at large.