Iran has arrested three suspects linked to the weekend suicide bombing in the southeastern province of Sistan-Beluchistan, the Fars news agency reported.
Provincial prosecutor Mohammad Marzieh told Fars Tuesday about the arrests of the three suspects but declined to give further details,
citing security reasons.
The three were the first to be arrested after Sunday's bombing, which killed 42 people including at least seven senior commanders of the Revolutionary Guards.
Another 28 were wounded and still in critical condition.
In New York, the UN Security Council issued a condemnation of the attack in the strongest terms. The body urged Iran to follow legal due process in investigating and prosecuting any perpetrators of the crime.
The attack has strained ties between Iran and Pakistan as the radical group Jundollah (Soldiers of God), which has already claimed responsibility for the attack, is based in neighbouring Pakistan.
The Mehr news agency reported Tuesday that two police officers were killed in Sistan-Beluchistan.
A local police spokesman said that the officers were killed by attackers in the provincial Iranshahr but refrained to give further details and did not say whether the deaths were linked to Jundollah.