* Government facing mounting criticism over explosion
* 12 killed, island's largest power facility destroyed
* Says suggestion explosives went to peacekeepers rejected
NICOSIA, July 12 (Reuters) - Cyprus had attempted several times to offload a dangerous cargo of confiscated Iranian munitions that blew up on Monday killing 12, but was rebuffed by the United Nations, a senior official said on Tuesday.
Attempting to fend off mounting criticism over Cyprus's worst peace-time disaster, authorities said they had tried in vain to get rid of the 98 containers of munitions they confiscated in 2009 from a ship sailing from Iran to Syria.
The entire cargo exploded on Monday, destroying the island's largest power facility and prompting the resignation of the defence minister and army chief.
"Our government's position in this difficult diplomatic issue was that the material not be held in Cyprus," said Stefanos Stefanou, the government spokesman.
He said, however, Cyprus had no choice but take the arms cargo in after its suggestions it went to the U.N. peacekeeping force in Lebanon was rejected, and it received no answer from the Security Council that the material be sent to Germany or Malta.
The economic impact of the disaster has yet to be assessed. Just a mangled shell remained of the 700 million euro power facility of Vassiliko on Tuesday, a station which provided Cyprus with 53 percent of its energy. The crisis triggered rolling power and water cuts.
Newspapers accused authorities of criminal negligence, pointing a finger of blame directly at Demetris Christofias, the communist president who was swept to power in 2008.
"(It was) a disaster that would have been avoided if our country was run by a less incompetent president," the liberal English language Cyprus Mail daily said in a front-page editorial.
The weapons-grade material confiscated was in violation of U.N. sanctions on Iran, and therefore the United Nations had to be involved in consultations about its fate, Stefanou said.
Cyprus had revisited the matter "from time to time" with the United Nations without success, he added.
Left stacked in scorching heat at a military base, one of the containers containing gunpowder had apparently expanded, letting off a "hissing noise" in the days preceding the blast, military sources said.
Warnings from officers to their seniors that it was a disaster about to happen went unheeded, relatives of the victims said.
However, it had never been discussed in cabinet meetings, Stefanou said. "The presidency was not aware of this," he said.
Two of the victims, twin 19 year old conscripts, had been assigned to douse the stack regularly with water to keep temperatures down, their family said.
"Which idiot decided to place 98 containers of explosives in a compound ... directly opposite the largest energy facility the Cyprus Republic now has?" the daily Politis asked, splashing the word "Criminals" on its front page.
"Whether the president was in oblivion, or is just scared of the responsibility, its difficult for him to convince us he can run this country." (Editing by Alison Williams)