The US state department has denied claims by Iranian officials that the US was involved in the bombing of a mosque in Iran which killed 25 people.
"We condemn this terrorist attack in the strongest possible terms," Ian Kelly, a state department spokesman, said on Friday of the attack on the mosque in the city of Zahedan a day earlier.
"We do not sponsor any form of terrorism in Iran. Never have, never will," he said.
About 125 people were also wounded in the attack which took place during evening prayers on Thursday.
Jalal Sayah, the deputy governor of Sistan-Baluchestan, the province bordering Pakistan and Afghanistan where the attack took place, said on Friday: "Hire of the terrorists by the US was verified based on investigation.
"The terrorists, who were equipped by America in one of our neighbouring countries, carried out this criminal act in their efforts to create religious conflict and fear and to influence the presidential election," he told state radio on Friday.
Iranians are due to go to the polls in two weeks to elect a new president.
'Inciting sectarianism'
Ayatollah Ali Khamenei, Iran's supreme leader, blamed "interventionist powers" for trying to incite sectarian conflict with the bombing, and the country's interior minister accused the US and Israel of being behind it.
Ali Reza Rongahi, Al Jazeera's correspondent in Iran, said a Sunni group known as Jundullah had claimed responsibility for several terrorist attacks and abductions in Sistan-Baluchestan in the past.
Iranian state television quoted Arabic news channel Al-Arabiya as saying the group claimed responsibility for the attack on Thursday, but this has not been independently verified.
"Whenever the Islamic Republic needs to prove to the world and the people that it is in control, there are attacks of this kind that aim to prove it cannot maintain peace and calm," Rongahi said.
On Friday, in Zahedan, armed men attacked the election campaign office of Mahmoud Ahmadinejad, the Iranian president, Zahedan wounding three people including a child, the official IRNA news agency said.
The attacks come two weeks before Ahmadinejad faces a tough election against three other candidates, two of whom are reformists who have criticised the president's performance and say they want to improve relations with the West.
