"Instead of make a proper use of nuclear energy at service of humanity, certain big powers misuse it," Ahmadinejad said in his speech to local residents of Semirom city in the central province of Isfahan, adding that "They have built bombs and dropped them on nations."

"These powers threaten other nations with their bombs," said Ahmadinejad, who was visiting Semirom on the fourth day of his five-day provincial tour of Isfahan.

He reiterated that his country is determined to use nuclear energy "in right way."

His remarks came just days after a report of the International Atomic Energy Agency (IAEA) to the United Nations Security Council (UNSC) said Iran still defied UNSC Resolution 1747 and expanded its uranium enrichment program.

The report, prepared by IAEA chief Mohamed ElBaradei, expressed concern about its "deteriorating" understanding of unexplored aspects of the program.

The report, which blamed Iran for blocking IAEA efforts to probe its nuclear activities, was handed over to the UNSC president for distribution among its members.

The UNSC unanimously adopted on March 24 Resolution 1747 with tougher sanctions to pressure Iran to suspend uranium enrichment activities.

Iran has refused to heed the council's demand, insisting that its nuclear programs are for peaceful purposes only.

The United States and some other Western countries have accused Iran of trying to develop nuclear weapons under the cover of its civilian nuclear programs.