International sanctions mounted against Iran with the European Union slapping asset freeze and travel ban on 37 individuals and 143 companies from the country on Thursday to counter Tehran's alleged clandestine efforts to build a nuclear bomb.

"The measures target entities and individuals directly involved in Iran's nuclear activities, which are in violation of UN Security Council resolutions; entities and individuals owned, controlled or acting on behalf of the Islamic Republic of Iran Shipping Line; and members of as well as entities controlled by the Islamic Revolutionary Guards Corps," according to an EU press statement.

An oil embargo against Iran is still being debated as Greece and other EU members dependent on Iranian oil fear the effect of such sanctions on their weak economies. But the ministers hope to arrive at a decision by January.

The EU sanctions reinforced those earlier imposed by the U.S., Canada and the U.K. in response to the International Atomic Energy Agency's recent report that Tehran's nuclear activities indicate construction of a bomb.

Tehran had denied the IAEA report branding it as a dictation from Washington to justify a possible military response to Iran. It insisted that the country's nuclear program is for peaceful purposes.

The new sanctions are also on top of earlier EU restrictions on new investment and technological assistance to Iran's gas producing and refining industry.

BBC diplomatic correspondent Jonathan Marcus doubts if the sanctions will affect the Iranian economy as Iran continues to trade with China and Russia, which are opposed to sanctions.

Meanwhile, Tehran has arrested nearly a dozen people who allegedly attacked the British embassy in the capital but later released all of them for unknown reasons, according to BBC.

The European Union headquarters in Brussels, Belgium.