Former president Hamid Karzai accused the United States of colluding with Daesh in Afghanistan and allowed the group to flourish in the country.
In an interview with Al Jazeera, Karzai said: "In my view under the full presence, surveillance, military, political, intelligence, Daesh has emerged."
"And for two years the Afghan people came, cried loud about their suffering, of violations. Nothing was done."
Karzai went on to say the US then used Daesh as an excuse to drop the Massive Ordnance Air Blast (MOAB) on Achin district in Nangarhar in April in a bid to destroy a tunnel complex being used by the group.
"And the next day, Daesh takes the next district in Afghanistan," he told Al Jazeera.
“That proves to us that there is a hand in it and that hand can be no one else but them [the US] in Afghanistan."
At the time, the US said had been designed to minimize the risk to Afghan and US forces conducting clearing operations in the area.
Karzai also condemned the attack at the time and said it was "inhuman and most brutal misuse" of Afghanistan as "testing ground for new and dangerous weapons".
Karzai also told Al Jazeera that he welcomed a recent call by the International Criminal Court (ICC) prosecutor to investigate war crimes in Afghanistan.
"She's right to launch such an investigation," Karzai said.
Karzai also acknowledged that there were human rights violations during his government.
"Definitely, there were violations by the Afghan security forces, by the US, and by others."
Karzai said he would help with any investigation, even into his own potential complicity.
"I have been asking for this so that they come to Afghanistan and investigate as to what has happened in this country."
During the interview, Karzai was also asked to respond to claims by human rights groups that he was warned while in office that human-rights abuses were taking place.
"They are wrong," he said. "They didn't tell me. I told them."
"I told the Western human rights bodies as to what was going on in Afghanistan. They were hiding it. The Western press was hiding it. I told them. I raised it," he said in the interview.