ISLAMABAD, Pakistan (CNN) -- Pakistan denied Wednesday that it is harboring a Sunni rebel leader accused of orchestrating a suicide attack in neighboring Iran.
Images from Iranian TV show debris and carnage from Sunday's suicide bombing.
Tehran has vowed "a crushing response" to the Sunni rebel group Jundallah for Sunday's suicide bombing in Sistan-Baluchestan province that killed 42 people. Iran has accused the United States and Pakistan of having links to Jundallah.
Iran has demanded Pakistan hand over Jundallah leader Abdul Malik Rigi, whom Tehran blames for plotting the attack. But Pakistani Interior Minister Rehman Malik said Wednesday that Rigi is in neighboring Afghanistan.
Iran's government-funded Press TV said Jundallah has claimed responsibility for the attack, which killed several key leaders of the elite Revolutionary Guard Corps.
Major Gen. Mohammad Ali Jafari, the Corps commander, said Monday that investigators have found documents connecting Rigi to security forces of the United States and Pakistan. Rigi's actions have "without a doubt been supported by these organizations," he said.
A U.S. State Department spokesman has called the accusations "completely false."
Iran summoned Pakistan's ambassador to its foreign ministry. There, he was told to urge his government to arrest the people behind the attack.
"We have heard that some of the government agents in Pakistan actually collaborate with the supporters of this savage act of terrorism, and we see it as very much within our rights to demand that they turn those criminals over to our nation," Iranian President Mahmoud Ahmadinejad said, according to the state-run Islamic Republic News Agency.
Pakistani President Asif Ali Zardari called on his Iranian counterpart, Ahmadinejad, on Monday to offer condolences and reaffirm his country's commitment to fighting extremism in the region, said a source inside the president's office.
Pakistan's foreign minister, Shah Mehmood Qureshi, said some Jundallah supporters already have been turned over to Iran.
"We have a good relationship with Iran and are committed in the fight against extremists. Why would we do anything that would damage and jeopardize our relationship?" he asked.
Iran observed a three-day mourning period to remember the people killed in the attack. A man carrying explosives blew himself up Sunday as participants headed to a conference between Shia and Sunni groups.
In the past, the predominantly Shiite central government in Tehran has accused Jundallah of fomenting unrest in the province. Iran has alleged that the United States and Saudi Arabia are funding the group. Jundallah says it is fighting for the rights of Sunni Muslims in the country.