The suicide bomber who allegedly carried out last week's deadly attack on Iranian security forces was a Pakistani national, local media quoted a senior military commander as saying.
"The suicide bomber was named Hafez Mohammad-Ali and was from Pakistan," Brigadier General Mohammad Pakpour of Iran's Islamic Revolutionary Guards Corps (IRGC) said on February 19, according to the force's Sepah news agency.
The head of the IRGC’s ground forces also said that another alleged member of the militant cell that planned the February 13 attack was also Pakistani.
Three Iranians from Sistan-Baluchistan Province in southeast Iran were also part of the cell and two of them have been arrested, according to Pakpour.
The guards on February 18 announced three arrests in the case.
Islamabad has condemned the attack in which 27 IRGC members were killed, one of the deadliest on Iranian security forces in years, and vowed to cooperate.
Pakistani Foreign Minister Shah Mehmood Qureshi said on February 19 that his country had handed over Iranian suspects.
"We will cooperate fully with Iran, we have operational contact with Iran," Qureshi told state-run television.
The Sunni group Jaish al Adl (Army of Justice), which says it pursues more rights and better living conditions for ethnic minority Baluchis in eastern Iran, claimed responsibility for the bombing.
In the attack, a suicide bomber drove an explosives-laden vehicle into a bus that was transporting IRGC troops in Sistan-Baluchistan Province -- a volatile area near Iran's borders with Pakistan and Afghanistan where militant groups and drug smugglers frequently operate.
The province is populated mainly by Sunni Muslim ethnic Baluchis.
Iran has repeatedly said that militant groups operate from safe havens in Pakistan and called on the neighboring country to crack down on them.
Tehran has also accused Saudi Arabia of inciting members of Iran's Sunni Muslim minority to violence.
Riyadh denies the accusation.