Former Taleban Foreign Minister Wakil Ahmad Mutawakil has arrived in the south-western Afghan town of Kandahar, after his release from the US military base in Bagram, reports say.
Mutawakil reportedly wanted Bin Laden to leave Afghanistan
A Pakistan-based aide to Mr Mutawakil said on condition of anonymity that the former minister was now staying with his relatives in the town after being freed about four days ago.
Mr Mutawakil spent some 18 months in US custody, following his surrender shortly after American troops ousted the Taleban regime in late 2001. The charges against him were never specified.
News of Mr Mutawakil's release came as Nato-led peacekeepers in Afghanistan and Afghan police said they had arrested a man suspected of planning terrorist attacks.
An spokesman said the man, identified as Abu Bakr, was a senior commander in Kabul for the Hizb-e-Islami faction led by the renegade warlord, Gulbuddin Hekmatyar.
Mr Hekmatyar - a former Afghan prime minister - has been labelled a wanted terrorist by Washington, and there have been reports that his faction may have formed a loose alliance with Taleban and al-Qaeda remnants.
In another development, the US envoy to Afghanistan, Zalmay Khalilzad, warned that Taleban militants may launch "more spectacular attacks" on American-led coalition forces there.
Speaking on the second anniversary of the US intervention in Afghanistan, Mr Khalilzad said the fight against terrorism was a long-term struggle.
He also welcomed the recent operation by Pakistani security forces against the Taleban and al-Qaeda, but said Islamabad should do more to stop cross-border attacks.
Mr Mutawakil has always been described as the more respectable face of the Taleban.
Just before the US sent troops to Afghanistan, he reportedly had a major disagreement with Mullah Mohammad Omar, founder of the Taleban movement, on sheltering Osama Bin Laden in Afghanistan.
It was reported that Mr Mutawakil led a group of moderate Taleban who wanted Bin Laden to leave Afghanistan to avoid US reprisals against the Taleban regime.
Before becoming the Taleban foreign minister, Mr Mutawakil had served as a spokesman and personal secretary to Mullah Omar.
The BBC's Rahimullah Yusufzai in Peshawar in Pakistan says it is not yet clear under what conditions Mr Mutawwakil was released.