TEHRAN, Iran — Iran said Monday it has decided where to build 10 new uranium enrichment sites inside protected mountain strongholds and will start construction on the first in March, defying international efforts to curb its nuclear program.

Enriching uranium creates fuel for nuclear power plants but can also, if taken to higher levels, produce the material for weapons and Iran's growing capacity in this process is at the centre of its dispute with the international community.

The UN Security Council has already passed four sets of sanctions against Iran to try and force it to stop enriching uranium.

Last year, Iran flouted international concerns by claiming it would build 10 new enrichment plants and Monday's announcement revealed that the sites had been chosen and would be inside mountains, without revealing any other details.

"Construction of a new uranium enrichment site will begin by the end of the (Iranian) year (March) or early next year," Vice-President Ali Akbar Salehi said. "The new enrichment facilities will be built inside mountains."

Revelations a year ago of a previously undisclosed enrichment facility in a secret mountain base near the city of Qom inflamed international suspicions over Iran's nuclear program and helped spur a fourth set of international sanctions in June.

The U.S. and its allies accuse Iran of using its civilian nuclear program as a cover to develop a nuclear weapons capability. Iran has denied the accusation, saying its nuclear program is geared merely toward generating electricity.

British Prime Minister David Cameron's spokesman Steve Field said that Salehi's announcement was a cause for concern. "The reports that we have seen this morning certainly do not give us any comfort that Iran is moving in the right direction," Field told reporters.

French Foreign Ministry spokeswoman Christine Fages, meanwhile, said the announcement "only intensifies the deep worries of the international community about the Iranian nuclear program."

"We want Iran to respect its international obligations by suspending all its activities of uranium enrichment," she said.

Iran has an industrial-scale, internationally supervised enrichment site in Natanz, in central Iran, with around 8,500 centrifuges and as well as the smaller one under construction near Qom. The Islamic republic said it needs 20 large-scale sites to meet domestic electricity needs of 20,000 megawatts in the next 15 years.

President Mahmoud Ahmadinejad on Monday also officially notified the government of the implementation of a new law banning the government from anything except the most minimum level of co-operation with the International Atomic Energy Agency, the UN nuclear watchdog.

The law is seen as a retaliation for the sanctions and also includes a provision authorizing the Iranian government to retaliate against any countries that attempt to search its ships or airplanes for dual-use materials with inspections of their own.

The Security Council resolution calls on, but does not require, all countries to co-operate in cargo inspections if there are "reasonable grounds" to believe the items could contribute to the Iranian nuclear program.

The Iranian law also requires the government to continue refining uranium up to 20 per cent to fuel a small medical research reactor in Tehran.

Enriching uranium to 20 per cent, instead of just the low levels required for fuel, puts Iran much closer to the 90 per cent level needed to create weapons grade material, further aggravating the Western powers.

A number of swap deals have been proposed in which other countries would handle the enrichment process and give Iran the enriched fuel, but a final agreement has remained elusive.