The international spotlight is back on Iran's nuclear program ahead of six-country talks in Berlin on possible new UN economic sanctions against Tehran.

At least five gas stations were set on fire by angry motorists in the Iranian capital, Tehran, today in protest against a government decision to begin rationing fuel. Long lines of cars formed at gas stations last night as people attempted to fill their gas tanks ahead of the midnight imposition of the rationing plan.

Tehran has condemned a recent warning by the Group of Eight (G8) industrialized economies that Iran could face more sanctions over its controversial nuclear program.

The U.S. State Department has warned Americans against traveling to Iran, accusing Tehran of a "disturbing pattern" of harassing Iranian-Americans. The warning comes after international human rights groups called on Iran to release two Iranian-American scholars -- Haleh Esfandiari and Kian Tajbakhsh -- and peace activist Ali Shakeri.

Independent academic and human rights groups today are demanding the immediate release of two Iranian-American scholars jailed in Tehran on charges of spying.

Iran today again insisted it will not agree to the key demand of Western powers about its controversial nuclear program. Iran's Foreign Ministry spokesman Mohammad Ali Hosseini says Tehran will not suspend uranium enrichment, a process the West fears could be used to make nuclear weapons.

President Mahmoud Ahmadinejad on Wednesday extolled what he described as Iran's self-sufficiency in producing army equipment and said Iran was so powerful now, no other country would dare launch a military strike against it.

Iranian President Mahmud Ahmadinejad said today that Tehran's response to any possible U.S. military attack would be "severe." Ahmadinejad made this comment at a news conference in the United Arab Emirates.

Compromise over Iranian controversial nuclear program was impossible if the West continued to demand Tehran suspend uranium enrichment. Ali Larijani's comments came a day after the U.S. and France took Iran to task during a conference on nuclear proliferation for defying a U.N. Security Council demand that it freeze enrichment.

Officials from six world powers are expected to meet for talks on persuading Iran to halt its sensitive nuclear work. The meeting in Berlin will involve senior diplomats from Germany and the five permanent United Nations Security Council members -- the United States, France, Britain, Russia and China.

Tehran's announcement on April 9 of industrial-scale nuclear enrichment is regarded by critics as a further act of defiance by a government that has resisted international pressure to suspend sensitive nuclear work.

Iranian parliament speaker Gholam Ali Haddad-Adel today said Britain was taking "more appropriate action" to end the dispute over Tehran's detention of the British naval personnel in the Persian Gulf on March 23.