A local official and an influential prayer leader in Iran's capital, Tehran, have each accused the United States of involvement in a deadly mosque bombing in southeast Iran.
Reports say some 20 people were killed and as many as 120 injured in the massive May 28 blast during evening prayers at a Shi'ite mosque in Zahedan, the capital of Iran's restive Sistan-Baluchistan Province, where many of the country's minority Sunnis reside.
The attack was one of the deadliest such incidents in decades in Iran, where local officials have occasionally accused Washington and its allies of operating through minorities to stir up trouble in remote border regions.
On May 29, U.S. Deputy State Department spokesman John O'Sullivan told Radio Farda that the United States had nothing to do with the bombing.
"First of all, we'd like to condemn this terrorist attack in the strongest possible terms. Any attack on innocent life is, frankly, unacceptable, especially when it is targeting people in a house of worship. I think it is even worse. But we also have to deny any of these allegations. The U.S. does not sponsor any form or terrorism," O'Sullivan said.
He added, "We deny the allegations. We've also noted a recent trend throughout the region, in Iraq, Iran, and even Pakistan, of bombings targeting Shia mosques. We really reject any kind of instigation toward sectarian violence. We hope that is not the case. Overall, the United States condemns any kind of terrorist attacks, especially when they target innocent civilians."
Sistan-Baluchistan's deputy governor, Jalal Sayah, told Iranian state radio that "the terrorists...were equipped by America in one of our neighboring countries" and said it was part of "efforts to create religious conflict and fear and to influence the presidential election" that is set for June 12.
Part of the mosque, which is said to be the second largest in the provincial capital, was also destroyed.
"There was a blast during the evening prayers at the Amir al-Momenin Mosque [in which] a number of the worshippers were martyred," said provincial governor Ali Mohammad Azad, adding that the injured had been transferred to local hospitals.
Iran has declared three days of mourning for the victims.
'Team Of Terrorists'
Azad said the Intelligence Ministry was interrogating members of "a Zahedan team of terrorists" who were arrested in connection with the bombing. He suggested they were planning to plant more bombs in other locations.
Hossein Sajedinia, a senior Tehran police chief, said one of the attackers was killed in the blast and another arrested.
A Sunni militant group, Jundallah (Soldiers of God), claimed responsibility for what it described as a suicide attack in an e-mail sent to RFE/RL. The group's claim could not be verified.
Jundallah has been behind attacks in the past in that area, including a 2007 roadside bombing in which more than 10 members of Iran's Islamic Revolutionary Guard Corps (IRGC) were killed.
The group has also claimed responsibility for the kidnapping and killing of Iranian soldiers.
Iranian officials have accused Jundallah of having ties to Al-Qaeda and aiming to create ethnic strife. The group says it is fighting for the rights of Iran's Sunnis, including the Baluch minority.
Tehran Friday Prayers leader Ahmad Khatami alleged to worshippers that "the hands of the U.S. and Israel" were "undoubtedly" involved the attack. He said "Wahhabis and infidel and evil Salafis" were accomplices a crime that was organized elsewhere."
Iranian officials have in the past accused U.S. and British forces based in the region of stirring up ethnic tension in Iran's border areas.
Conservative presidential candidate Mohsen Rezai, a former head of the IRGC, called the Zahedan attack a move to by Iran's enemies to create fear and diminish people's participation in the upcoming election.
Iran's leading reformist presidential candidate, Mir Hossein Musavi, was quoted by agencies as saying that incidents like the mosque bombing "have been either influenced or supported by foreign forces."
The other reformist presidential candidate, Mehdi Karrubi, said that one of the aims of the blast was to discourage people from participating in the June vote.
Sistan-Baluchistan, which has a large Baluchi minority, is one of Iran's most deprived regions.
The region is a major route for drug trafficking and the scene of frequent clashes between police forces and drug smugglers.
RFE/RL's Radio Farda contributed to this report