A total of 143 entities and 37 individuals will be subject to an asset freeze and travel ban within the EU, an official statement said, with further details to be released Friday.
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The EU is also contemplating additional measures aimed at "severely affecting" Iran's financial system, transport and energy sectors, its statement said.
EU foreign ministers debated whether to impose an embargo on Iranian oil but could not reach an agreement, the Associated Press reported.
Britain, France, Germany and Sweden are in favor of oil sanctions but Spain, Greece and Italy object, an unnamed EU diplomat told Agence France Presse. Greece in particular is said to be dependent on Iranian oil, which the heavily-indebted country is allowed to buy on credit, the source said.
Iran was the EU's fifth-largest oil supplier in 2010, according to AFP.
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Britain is believed to have led the calls for tougher action against Iran.
Ahead of Thursday's talks, UK Foreign Secretary William Hague said he wanted "an intensification of the economic pressure" on the Iranian government, but denied the move was in retaliation for an attack on the British embassy in Tehran Tuesday.
He told BBC radio:
"These are not measures that are in reaction to our embassy. [...] Our long-term concern is, of course, the nuclear programme, the danger that poses to the peace of the Middle East and the wider world, the threat of proliferation spreading to other countries in the region."
Hague also alleged there was "a link between what is happening in Iran and what is happening in Syria," the Guardian said.
The EU condemned the embassy attack and promised to take "appropriate measures" in response.
The new sanctions come on top of the EU's asset freeze on hundreds on Iranian companies and its measures to block new investment in Iran's gas industry, the BBC said.
Last week the UK halted all its financial dealings with Iranian banks over fears about Tehran's nclear ambitions.
Iran denies its nuclear program is for anything but peaceful purposes.
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