At Bagram Airbase outside of Kabul, a dawn flag-lowering ceremony was held with the Stars and Stripes raised over the base and then immediately lowered to half-staff.
Shortly before the ceremony several shots were fired at the base by an Afghan gunman and in the eastern town of Khost an airfield used by U.S. forces was hit by rocket fire.
Neither attack caused any casualties among U.S. personnel although they provided a stark reminder of the continuing threat posed to the American presence in Afghanistan.
Bagram is the main U.S. base for operations in Afghanistan and is home to around 8,000 soldiers in the country to hunt remnants of the former Taliban regime and members of Osama bin Laden's al Qaeda network.
The whereabouts of bin Laden himself and Taliban leader Mullah Omar remain unknown 11 months after the U.S.-led campaign in Afghanistan began.
In Kabul itself meanwhile security forces are on high alert for the 9/11 anniversary although officials say they had received no specific threats.
The city was scene last Thursday to a powerful car bomb attack that left 26 people dead and wounded dozens more.
According to military officials involved in Operation Champion Strike eight of the detainees were captured Saturday when troops raided a suspected al Qaeda and Taliban recruitment center near Afghanistan's border with Pakistan.
Among the eight were two suspected al Qaeda members, including the financier, and one man identified by the soldiers as a "high-value target."
A U.S. soldier said he overheard one of the two men transmit a radio message before he was captured during which he said, "I'm surrounded by the Americans, I've got no way out."
The troops confiscated what one soldier described as a "bucketful of satellite phones, passports, a poster of Osama bin Laden, and Taliban and al Qaeda documents."
In the second search, CNN's Ryan Chilcote accompanied the 1st Batallion -- also known as the "Red Devils" -- to the village of Sharip Khail, not far from the first targeted area.
There, members of the Afghan Militia Force were fired on by unidentified gunmen as they detained a man in a residential compound.
'On the run'
A U.S. Army sergeant told the village elder, "We are here to search your village ... we are not hear to take your things ... you have 10 minutes to get all the men, women and children here, don't leave anyone behind."
After the village was emptied, the soldiers found AK-47 rounds in a mound of hay and, noticing a portion of newly mud-plastered wall, dug through to find 17 rockets and documents inside, including a postcard with Taliban leader Mullah Mohammed Omar's name written on it and a document from the Pakistani Foreign Service.
They also found rosters of names, Korans, English learning manuals, hand grenades and an anti-tank mine.
"I think that we've got those who oppose peace on the run over here," said Lt. Col. David Gerard, the battalion commander for the Red Devils.
"We want to deny Afghanistan and other countries for that matter from providing sanctuary or a place to train. But the fact that they are on the move is preventing them from planning future attacks."
He added that capturing Osama bin Laden wasn't the only goal although "capturing him would mean a lot to the American people."
"We've been fighting terrorism for over 22 years and it didn't just start on September 11," Gerard said.
-- CNN Correspondent in Afghanistan Ryan Chilcote contributed to this report
Reuters contributed to this report.