(CNN) -- Two alleged suicide bombers were responsible for a pair of explosions in the southeastern Iranian city of Zahedan that left at least 20 dead and scores wounded, Iran's state news agency IRNA reported Thursday.

The first blast occurred at 9:20 p.m. (12:40 p.m. ET) in front of the city's Grand Mosque, and the second explosion followed within minutes, IRNA said.

The news agency reported that at least 20 people were killed and 100 were wounded. Iran's state-run Arabic channel, Al-Alam, reported that at least 30 were killed and more than 50 wounded.

"It is not yet possible to announce the exact number of those killed and injured in the incident," a police official said, according to IRNA. Zahedan is the capital of Sistan-Baluchestan province, which borders Pakistan.

Iranian Deputy Interior Minister Ali Abdollahi labeled the incident a terrorist act, the semi-official Fars news agency said.

"Terrorist operations in Zahedan have left several dead and injured," Abdollahi said, according to Fars.

"More information will be given when our investigations are completed," he told Fars.

In Washington, U.S. Secretary of State Hillary Clinton condemned the attacks. "The United States extends its sympathy to the families and loved ones of those injured and killed," she said in a statement. "We also call for the perpetrators of this horrific attack to be held accountable for their actions."

A lawmaker in Zahedan told IRNA that "the two explosions were the result of suicide bombings. First, someone in a woman's clothing tried to enter the Jam-e Mosque in Zahedan but was prevented from entering."

It was not immediately known whether that person was a man or a woman, said Hosseili Shariari, a Zahedan member of parliament.

Three or four people died in the first explosion, and while people were trying to help those victims, the second suicide bomber detonated his explosives, he told IRNA.

Shariari blamed the followers of two extremist groups, the Wahhabis, followers of an extremist Saudi Arabian sect, and the Jundallah, followers of Abdolmalek Rigi, who was responsible for suicide bombings in the past.

"These explosions were quite predictable," Shariari said, according to Fars. "I have said many times at press conferences that the remaining agents of the Wahhabis and the Rigi group are determined to conduct this kind of operation to prove that they still exist."

Last October, in the same province, a suicide bomber blew himself up as participants headed to a conference between Shia and Sunni groups in the city of Sarbaz.

At least 29 were killed in that bombing, including five senior officers of Iran's elite Revolutionary Guard Corps.

The terrorist group Jundallah -- also known as the People's Resistance Movement of Iran -- claimed responsibility for that attack.

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 that it is fighting for the rights of Sunni Muslims in the country.

CNN's Shirzad Bozorgmehr contributed to this report.