Afghanistan says it has arrested a Pakistani intelligence agent who acted as a key link with al-Qaeda leaders.
Afghanistan blames Pakistan for Taleban attacks
Presidential spokesman Karim Rahimi said the agent had been detained in eastern Kunar province carrying documents which proved his guilt.
The news came a day after intelligence officials said an Afghan general had been arrested for spying for Pakistan.
Afghanistan has long blamed Pakistan for cross-border attacks by the Taleban. Islamabad denies the charges.
'Bin Laden escort'
Mr Karimi named the man arrested as Sayed Akbar, who he said worked for Pakistan's controversial Inter-Services Intelligence (ISI) agency.
"Some evidence and documents have been seized with him proving his destructive activities in Afghanistan," Mr Karimi told a news conference in the capital, Kabul.
Sayed Akbar comes from the Chitral region of northern Pakistan bordering the Afghan province of Nuristan, the spokesman said.
The BBC's Payenda Sargand in Kabul says, according to the Afghan authorities, Mr Akbar was in charge of relations between the ISI and al-Qaeda leaders.
Officials say he has confessed to his "illegal activities" in Afghanistan. These are said to include escorting Osama Bin Laden last year from Nuristan to Chitral.
Pakistan's foreign ministry called the allegations baseless and said it had requested more information and for diplomats to be allowed to see the man.
On Monday, intelligence officials in Kabul said they had arrested an Afghan army general, Khair Mohammed, on charges of selling secrets to the ISI.
Mr Rahimi told the news conference: "National security officials arrested a defence ministry general committing national treason, spying for foreigners, and he is under investigation."
Correspondents say it is not clear if the two arrests are linked. The defence ministry issued a statement saying that Khair Mohammed had not worked for it for almost four years.
He denied the charges against him.
Relations between Afghanistan and Pakistan have been tense for years, but have worsened during 2006 as violence in Afghanistan has soared.
Last week, President Hamid Karzai publicly accused the Pakistani government of backing the Taleban and said it wanted to turn Afghans into "slaves".
Afghanistan says Taleban leaders plot some of their attacks on Afghan targets from Pakistani soil.
Pakistan was once the Taleban's main sponsor, but after the September 2001 attacks in the United States Islamabad joined the US-led "war on terror".
The Pakistani government denies it continues to support the militants or that it could do more to stop them crossing the porous border, and points to the deaths of hundreds of Pakistani troops fighting pro-Taleban militants in the country's tribal areas.
The authorities say that more than 3,500 people have been killed in Afghanistan in 2006 - the bloodiest year since US-led troops ousted the Taleban five years ago.