Iran is claiming terrorists with links to the United States and Britain carried out a mosque explosion that killed 14 after earlier blaming the blast on leftover explosives from an event commemorating the Iraq-Iran war, Reuters reported on Thursday.

"The blast ... was caused by a bombing by a terrorist group with links to Western countries, especially Britain and America," the ISNA news agency quoted Intelligence Minister Gholamhossein Mohseni-Ejehi.

Officials said they had arrested six people who were found with weapons and had "intended to carry out similar acts in other places," said Mohseni-Ejehi, alleging that when given intelligence on the suspects, Western nations ignored Iran’s appeal for action and instead supported the six, Reuters reported. The main suspect still was at large, he said.

Some 200 of the 1,000 people packed into the mosque were injured in the April 12 blast. The holy house in Shiraz, about 559 miles south of Tehran, was the site of a recent military exhibition.

One day after the blast, the police chief of southern Fars Province, Gen. Ali Moayyedi, said the explosion was not a bombing and rejected links to "any sort of insurgency."

Moayyedi, in comments carried by state IRNA news agency, said the initial investigation found remnants of ammunition from the military exhibition.

Iran has repeatedly accused the U.S. and Britain of backing militants and ethnic opposition groups to destabilize the Tehran government. Both countries have denied the accusations.

Tensions between Iran and the West have grown over U.S. allegations of Iranian involvement in attacks on American troops in Iraq and over suspicions that Tehran is trying to develop nuclear weapons.

Bombings are unusual in Shiraz, where tourists come to see the ruins of nearby Persepolis, an ancient Persian kingdom that was a center for ceremonies and worship.

The mosque is part of the Rahpouyan-e-Vesal cultural center in Shiraz. The blast went off as the mosque's cleric was delivering a weekly speech denouncing the Bahai faith and Wahabism — an austere brand of Sunni Islam practiced mostly in Saudi Arabia, according to local news reports. Such speeches are not unusual in Iranian mosques.

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The Associated Press contributed to this report.