Afghanistan and Iran announced Sunday plans for enhanced security cooperation to combat threats from the Islamic State group, including possible joint military operations.
Standing alongside visiting Afghan leader Ashraf Ghani, Iran's President Hassan Rouhani said the tumult hitting the region meant intelligence must be shared.
His comments came after IS, which holds swathes of Syria and Iraq, said it was responsible for a suicide bombing in Afghanistan's eastern city of Jalalabad which killed 33 people.
The attack on Saturday at a state-owned bank where government workers were drawing their salaries was the first in Afghanistan claimed by IS. More than 100 people were also wounded.
Ghani's two-day visit to Iran is his first since taking over from president Hamid Karzai in September, and he was accompanied on the trip by his foreign minister and minister for oil and mines.
The Afghan leader has repeatedly raised the prospect of IS making inroads in his country, though the jihadist group has never formally acknowledged having a presence in Afghanistan.
