Iran deployed warplanes and missiles on Monday in an ‘exercise’ to protect nuclear sites threatened by possible Israeli attacks and warned it could cut oil exports to more EU nations unless sanctions were lifted.

The stance marked a hardening of the Islamic republic's defiance in an international standoff over its nuclear programme -- and suggested it was readying for any eventual confrontation.

The moves were announced the same day as officials from the UN nuclear watchdog agency arrived in Tehran for a second round of talks they said were focused on ‘the possible military dimensions of Iran's nuclear programme.’

Iran, while holding out hope of reviving collapsed negotiations with world powers, has underlined it will not give up its nuclear ambitions, which it insists are purely peaceful.

Much of the West and Israel, though, fear Iran's activities include research for atomic weapons.

The United States and Europe have ramped up economic sanctions against Iran's vital oil sector, while Israel has fuelled speculation it could be on the brink of carrying out air strikes on Iranian nuclear facilities.

Iran's military said in a statement on Monday that it has launched four days of manoeuvres in the south of the country aimed at boosting anti-air defences to protect nuclear sites.

Missiles, anti-aircraft artillery, radars and warplanes were being deployed in the exercise it dubbed "Sarollah", a word borrowed from the Arabic meaning "God's vengeance".

"These manoeuvres aim to reinforce the coordination between the military and the Revolutionary Guards for a total coverage of the country's sensitive facilities, especially nuclear sites," the statement said.

At the same time, the deputy oil minister, who also runs the National Iranian Oil Company, warned that a cut in Iranian oil exports announced on Sunday against France and Britain could be expanded to other EU nations.

"Certainly if the hostile actions of some European countries continue, the export of oil to these countries will be cut," said Ahmad Qalebani, pointing the finger at Spain, Greece, Italy, Portugal, Germany and the Netherlands, according to a Mehr news agency report.

Iran exports about 20 percent of its crude -- some 600,000 barrels per day (bpd) -- to the European Union, most of which goes to Italy, Spain and Greece.

Although the export halt for France and Britain was largely symbolic -- neither country imports much Iranian oil -- prices on world markets soared on fears the cuts could be expanded before Europe secured other supplies.

Brent North Sea crude for delivery in April was trading at $120.55 a barrel on Monday, after hitting a nine-month high before inching back a little. New York's main contract, West Texas Intermediate light sweet crude for March, moved up to $104.85.

Iran's defiance included another pointed military deployment: that of two Iranian warships that state television said had docked in Syria to help train that allied country's sailors.

Their presence in the Mediterranean, close to Israel, unnerved the Jewish state, which said it "will closely follow the movement of the two ships to confirm that they do not approach the Israeli coast."

Iran has also flaunted what it said was "major" nuclear progress, declaring it was adding thousands more centrifuges to its uranium enrichment activities and producing what it said was 20-percent enriched nuclear fuel.

The UN nuclear watchdog, the International Atomic Energy Agency, in November issued a report voicing strong suspicions that Iran was researching an atomic weapon and missile warheads.

Last month it confirmed that a new, fortified uranium enrichment plant outside Iran's holy city of Qom had been activated.

The West has ratcheted up its sanctions to try to force Iran to stop enrichment, but with no success so far.

Meanwhile, the assassinations of three Iranian nuclear scientists and attempted bomb attacks against Israeli diplomats in several countries have pointed to a possible covert war between the two Middle East arch foes.

But for all its flexing and posturing, Iran has also formally agreed to an EU overture to revive talks with world powers that collapsed a year ago.

However, the head of Iran's Atomic Energy Organisation, Fereydoon Abbasi Davani, told Al-Alam television that the powers -- the so-called P5+1 group consisting of the five permanent UN Security Council members plus Germany -- should let up with the pressure.

"They would do better to change their method, because what they've used in the past hasn't met with success," he said.

Abbasi Davani also taunted Israel, which he said was "afraid of the progress we've made in the nuclear field."

The official, who escaped an assassin's bomb in 2010, said: "They have done all they can, killing our nuclear scientists. If they haven't attacked Iran by now, it's because they're not able to do so."