American troops have launched a major military operation in southern Afghanistan, said to be one of the largest in over a year.
Soldiers from the army's 82nd Airborne Division are being used in the assault near the city of Kandahar, where they are believed to be looking for members of the al-Qaeda network.
Bin Laden - officials in Pakistan say he is not in their country
Up to 1,000 US troops are searching for Osama Bin Laden and members of his terror network in Afghanistan.
They are also looking for members of the former Taleban regime, which was based in Kandahar.
"The White Devils of Coalition Task Force 82 began Operation 'Valiant Strike' with an air assault at 6 am this morning (0130 GMT)," the US military said in a statement issued at the Bagram air base in Afghanistan.
"Valiant Strike will consist of offensive operations south east of Kandahar."
US military spokesman, Colonel Roger King told reporters the troops were pursuing "specific objectives".
The attack took place as US forces in the Gulf began bombing Baghdad at the end of a 48-hour ultimatum to Saddam Hussein.
However, Colonel King said: "There is no connection. Operations in Afghanistan are conducted independently of any operation in other sectors."
He said that preparations for the operation had been going on for several months.
Reports from the Pakistani side of the border with Afghanistan say the US operation came after unidentified attackers killed three Afghan soldiers on Wednesday.
The incident took place at night at the Sharobo checkpoint in the Shin Narey area, near the Pakistan border north of the town of Spin Boldak.
Afghan forces are reported to have arrested nine people in connection with the attack.
Military spokesman, Lieutenant Coryll Angel told the AP news agency that it is expected the operation in southern Kandahar will last for two or three days.
Raids on suspected al-Qaeda hideouts in Afghanistan and across the border in Pakistan have increased in recent weeks following the capture of one of the network's key figures.
Khalid Sheikh Mohammed was arrested in the Pakistani city of Rawalpindi earlier this month.
He is suspected of being the mastermind behind the 11 September attacks, and is now in US custody.
Officials say Mohammed has been providing details to his interrogators and that subsequent arrests have taken place on a basis of this information.