Iranian security forces have arrested suspects in a suicide bombing that killed at least 42 people, including senior Revolutionary Guard commanders, Iran's police chief said Wednesday.

Gen. Esmaeil Ahmadi Moghadam said members of the Sunni rebel group known as Jundallah, or Soldiers of God, that carried out Sunday's deadly bombing entered Iran from neighboring Pakistan. The group has waged a low-level insurgency in Iran's southeast in recent years, claiming to fight on behalf of the Baluchi ethnic minority, which it says is persecuted by Iran's government.

"Fortunately, a number of elements linked to this terrorist group were arrested by security forces," Moghadam was quoted as saying by the official IRNA news agency. He did not say how many were arrested.

Sunday's attack killed 15 members of the powerful Revolutionary Guard, including five senior commanders, and at least 27 others in the town of Pishin near Iran's border with Pakistan.

The dead included the deputy commander of the Guard's ground force, Gen. Noor Ali Shooshtari. The attacker targeted a meeting of Guard chiefs and local tribal leaders that was aimed at promoting unity between Iran's majority Shiites and minority Sunnis.

In a statement posted Wednesday on Jundallah's Web site, the group said those whom Iran had arrested were innocent and the only person involved in the attack was the bomber.

"Because of the weakness of the regime and its defeat, they arrest innocent people and under torture they will get false confessions," the Jundallah statement said.

Iran has accused the United States, Britain and Pakistan of having links with the Sunni militants of Jundallah, though all three nations have denied the allegations.

The accusations put strains on a traditionally friendly relationship between Iran and Pakistan that has soured in recent years over the issue of Islamic extremism. Iran's president and the Guard chief, for the first time, publicly accused Pakistan's intelligence service this week of supporting Jundallah.

Moghadam said talks between the two nations were taking place to discuss the arrest of those responsible for the attack.

"Unfortunately, some of the Pakistani intelligence services provided support for this group to carry out this terrorist attack," IRNA quoted him as saying. "Pakistan has a direct responsibility for this terrorist act and must provide the necessary facilities to track down and arrest the destructive elements."

Pakistan's interior minister said Wednesday that his nation was cooperating with Iran and has handed over a dozen suspected militants in recent months, including the brother of Jundallah's leader, Abdulmalik Rigi.

Iranian state media reported earlier this year that the Jundallah leader's brother was in custody and was to have been hanged along with 13 other members of the rebel group on July 14 but that his execution was postponed without explanation.

The Pakistani interior minister, Rehman Malik, told reporters in televised comments that Rigi himself was not in Pakistan, but in Afghanistan.

"I can tell you this with full responsibility, he is in Afghanistan. And I have given his exact location to the interior minister of Iran — where he is in Afghanistan," Malik said.

He pledged Pakistan's willingness to cooperate with Iran.

"We have told them they should work with us," he said. "We have seen many 9/11s and many such terrorism acts. We are the prime victim and we desire that our neighbors must not suffer from this pain."

Iran believes the U.S. and Britain are provoking ethnic unrest in Iran to undermine its security, charges Washington and London have denied.

The region in Iran's southeast has been the focus of violent attacks by Jundallah. The group accuses Iran's Shiite-dominated government of persecution and has carried out attacks against the Revolutionary Guard and Shiite targets in the southeast.

Iranian officials have accused Jundallah of receiving support from Al Qaeda and the Taliban, though some analysts who have studied the group dispute such a link.

Jundallah's campaign is one of several small-scale ethnic and religious insurgencies in Iran that have fueled sporadic and sometimes deadly attacks in recent years — though none have amounted to a serious threat to the government.