"Twenty-four foreign fighters were captured on Saturday. From our initial intelligence, they are Sudanese, Egyptian and Tunisian," US intelligence officer Captain David Bryant said.
According to the US military, a total of about 50 fighters have been arrested since thousands of US and Iraqi troops poured into Samarra on Friday, in one of the largest post-war operations in Iraq and the first major push to reclaim rebel-held enclaves before January's general elections.
It said up to 150 people were killed in the early stages of the fighting, most of them insurgents.
Bryant said the 24 foreigners were all caught in the same building and were carrying papers identifying them as chicken farmers, tea sellers or electricians.
Bryant also confirmed the existence in Samarra of a cell for top US foe Abu Musab al-Zarqawi's Tawhid wa Jihad group, which has been behind some of the deadliest attacks and a series of hostage-takings in Iraq.
He said the cell was thought to comprise about 25 members, all of them Iraqis and belonging mainly to the same tribe, but added that none of them had been captured yet.
The US military says Iraqi forces
are co-ordinating operations
A senior military spokesman could not confirm to Aljazeera.net the number of fighters captured, their nationalities or where they are being held.
"Iraqis are the ones who are leading this co-ordinated effort," said the spokesman.
An Iraqi ministry of defence spokesman could not be reached for comment.
Reports further state that US Captain Andy Lyman said the bulk of the fighting in Samarra was over and that the city was largely under control on Monday, but added that US and Iraqi troops were continuing their searches.
"Until now, we haven't captured any of the ringleaders," he said.
"It's only now that we're finding out who they are, based mainly on human intelligence, on tips coming from residents and received mainly by Iraqi forces, who are also conducting most of the raids."
Armed groups to unite
On Monday a Kuwaiti daily reported that groups fighting US-led troops in Iraq plan to unite under one umbrella.
"Very soon, these groups will combine their efforts under a single jihad banner, governed by a shura (consultative) council authorised by religious scholars," the Al-Rai al-Aam newspaper said citing sources "very close" to Iraqi "jihadi" groups.
There is a $25-million bounty on
Abu Musab al-Zarqawi's head
The new grouping would command a total of "7000 fighters spread all over Iraq", the paper said.
Representatives of the Sunni groups are currently visiting a number of Muslim countries to consult with leading clerics about their plans, it added.
The proponents of the new alliance plan to demand an end to sectarian attacks by al-Zarqawi's Tawhid wa Jihad group, particularly against Iraq's Shia majority, the paper said.
"If al-Zarqawi does not abandon his plans to instigate a sectarian rift, the groups will force him to do so even if that requires taking up arms against him," the paper quoted one of its sources as saying.
Another Kuwaiti daily, Al-Qabas, quoted Gulf intelligence sources as saying that al-Zarqawi's group had recently requested help in the form of "money and men" from unnamed Gulf groups.
The request was made after US and Iraqi forces managed to strike the group and cut its supply lines, the paper said.
It was the second report in recent days of moves by Iraqi armed groups to unite.
On Sunday, a statement reportedly posted on a website said a "unified command of the mujahidin" in Iraq had been formed as an umbrella for 10 groups, but its authenticity could not be independently verified.