TEHRAN, May 17--Iran's Intelligence Ministry said on Saturday US agents had armed and trained those behind a deadly blast in a mosque last month and that pipelines in the country's oil-rich south were also among the planned targets.

Washington and London have been blamed by Tehran of trying to destabilize Iran by supporting rebels, mainly those in sensitive border areas.

Intelligence Minister Gholamhossein Mohseni-Ejei had said 15 people had been arrested in connection with the blast and they had also plotted to attack a Russian consulate in northern Iran.

His ministry issued a new statement on Saturday, saying one of those behind the bombing was killed in an arrest operation.

"This network that the Americans had armed with different terrorist tools such as chemicals, explosive materials, dangerous and poisonous cyanide ... was guided directly by Americans agents into Iran," it said in a statement carried by the official IRNA news agency.

It said confessions of those arrested "show that American agents had told members of this network that their main mission was to spread fear among people in different cities".

Blowing up southern oil pipelines was among the group's targets and this was why "American centers had set up diving classes for this network to identify oil pipelines in the Persian Gulf", the statement said.

Weapons, explosives and maps were among item seized from those arrested, the Intelligence Ministry said.

Security is normally high in Islamic republic of Iran and such attacks have been rare after the Iraq-Iran war.