"As reported by Afghan officials yesterday, I can confirm that coalition forces are conducting military operations in the Zormat region of southeastern Afghanistan," Roger King, a spokesman at Bagram Air Base north of Kabul, told reporters.
CBS News Correspondent Tom Fenton reports three people have been detained and several small caches of arms were found.
King said the aim of the operations was to "find, capture or kill any remaining al Qaeda fighters and their supporters in the area and to deny the enemy sanctuary in that area."
He said the allied forces consisted of coalition conventional troops, special operations and Afghan militia forces, but gave no other details.
The area is located about 65 miles south of Kabul near the scene of fighting during Operation Anaconda in March. Anaconda was the largest U.S. ground operation of the Afghan conflict.
On Tuesday, an Afghan military chief in the area, apparently describing the same operation, said American and Afghan forces had detained four people in a door-to-door sweep through a town in the region believed to be loyal to a leading ex-Taliban commander.
Thousands of U.S. and coalition troops are in Afghanistan hunting the remnants of the former ruling Taliban and the al Qaeda network, blamed for the September 11 attacks on New York and Washington.
Afghanistan's defense minister said on Wednesday the operation had been launched against suspected bases of the Taliban and al Qaeda around the southeastern city of Khost.
The minister, Mohammad Fahim, also said he believed former Taliban leader Mullah Mohammad Omar was still alive and that Saudi-born al Qaeda leader Osama bin Laden, accused of masterminding the Sept. 11 attacks, was "probably" alive too.
U.S. and Afghan forces have worked together in the past to pursue remnants of the Taliban and the al Qaeda network, but the presence of U.S. troops acting alone in Afghanistan has caused confusion and resentment.
Fahim, who gave no further details about the operation, rejected criticism from abroad that the government of President Hamid Karzai only had real control in the capital of Kabul. However, he said al Qaeda had regrouped in areas along Afghanistan's southern border with Pakistan.
Asked why neither Mullah Omar or bin Laden had been caught nearly 11 months after the launch of U.S. operations in Afghanistan, Fahim said they most likely lived like nomads or in secret "like thieves" in tribal regions of Pakistan "and sometimes probably in border areas of Afghanistan."
The United Nations in Afghanistan said on Thursday it had failed in an attempt to disarm two warring factions in a disputed northern town.
A U.N. spokesman said the situation in the town of Goosfandi in Sari Pul province had proven "much more complex" than expected since U.N officials brokered a truce between the faction of Uzbek warlord General Abdur Rashid Dostum and Ustad Atta's Jamiat-e-Islami.
"The parties are still working...to find a mutually acceptable solution," Manoel de Almeida e Silva told a news briefing.
But he said a U.N team sent to the area at the weekend from the key northern city of Mazar-i-Sharif to supervise the disarmament was now returning.
A clash between the factions based on an old feud claimed at least eight lives earlier this month in Goosfandi.
Also Thursday, King said an investigator from the U.S. special operations force was looking into an incident in which Afghan militiamen hung the body of a man they shot during a firefight from a post for two hours near Kandahar.
The man, hired to guard a checkpoint near the Kandahar air base, opened fire on the militiamen Tuesday morning, killing two. The shooter was killed in return fire.
King said the U.S. forces asked the Afghan militia to dispose of the body properly "and conveyed our objections to this type of behavior."