Defiant in the face of Western pressure over its nuclear program, Iran says it has begun loading its first domestically made nuclear fuel rods into a research reactor in north Tehran.
The installation ceremony was led by President Mahmud Ahmadinejad.
In comments made to state television, Ahmadinejad said Iran has added 3,000 more centrifuges to its uranium-enrichment effort. He said there were now 9,000 working centrifuges in the program.
Ahmadinejad called the move “a sign of Iranian scientists' achievements."
Ahmadinejad also refuted Western accusations that Iran's nuclear program was aimed at making atomic weapons, a claim that has been repeatedly denied by Tehran.
"[Western criticism of Iran's nuclear program] is just an excuse," Ahmadinejad said. "If we put it aside, they would find another pretext. They say they want to talk to us. Are you really willing to negotiate with us? Or do you want to put us behind the negotiating table and tell us, 'Sign under whatever I tell you.'? Is that called a negotiation?"
Meanwhile, in a speech broadcast on state television, the head of the Atomic Energy Organization, Fereydoon Abbasi Davani, said Iran has activated the first cascade of a new, faster generation of centrifuges.
Davani said the centrifuges will increase Iran's capacity to enrich uranium by three times.
The Fars news agency reported that the new centrifuges, said to be domestically produced, were installed at the Natanz nuclear site.
Iran says it is enriching uranium for civilian purposes, including cancer treatment.
The moves come amid growing tensions over what the West sees as attempts by the Islamic republic to develop nuclear weapons.
The UN's International Atomic Energy Agency (IAEA) has said it believes the Tehran research reactor is among the Iranian facilities being used to pursue a nuclear weapons program.
In another development, state television reports that Tehran has reduced oil exports to six European countries in response to European Union sanctions over its nuclear program.
The move follows a meeting on February 15 between Iranian officials and six European ambassadors over the EU energy and financial sanctions imposed last month.
The Associated Press reports that the six affected countries are France, Greece, Italy, Portugal, the Netherlands, and Spain.
A European Commission energy spokesperson, responding to the announcement, said any affected EU states would turn to Saudi Arabia and other suppliers in the instance of an Iranian oil cutoff.
Europe currently accounts for 18 percent of Iran's total crude exports.
Meanwhile, a spokeswoman for the European Union's foreign affairs chief confirmed Wednesday that Catherine Ashton had received a letter from Iran.
Earlier on February 15, reports said Iran had also sent a letter to the European Union, saying it was ready to resume nuclear talks with world powers.
The official Islamic Republic News Agency said Iranian chief nuclear negotiator Saeed Jalili had written to Ashton saying Iran was ready to resume stalled negotiations on the nuclear issue with the so-called P5+1 group -- the five permanent UN Security Council members -- Britain, China, France, Russia, and the United States -- plus Germany.
The last talks between the P5+1 and Iran occurred one year ago in Istanbul and produced no results.
The moves by Iran come as Israel stepped up its war of words against Tehran
, accusing the country of masterminding this week's bomb plots in Thailand, India, and Georgia.
Iran has denied any involvement in the blasts, calling the accusations "baseless."
Compiled from agency reports