The United Nations Security Council has approved new sanctions against Iran over its suspect nuclear programme.

US President Barack Obama said the sanctions were the toughest Iran had ever faced. They took months of difficult negotiations by the five veto-wielding permanent UN Security Council members - the US, Russia, China, Britain and France - and non-member Germany.

The new resolution bans Iran from pursuing "any activity related to ballistic missiles capable of delivering nuclear weapons," bars Iranian investment in activities such as uranium mining and prohibits Iran from buying several categories of heavy weapons including attack helicopters and missiles.

It imposes sanctions on 40 Iranian companies and organisations - 15 linked to Iran's Revolutionary Guard, 22 involved in nuclear or ballistic missile activities and three linked to the Islamic Republic of Iran Shipping Lines. That more than doubles the 35 entities that had been subject to an asset freeze.

Mr Obama said the sanctions were "an unmistakable message about the international community's commitment to stopping the spread of nuclear weapons".

Britain's Ambassador Mark Lyall Grant said: "All those measures can be suspended and eventually eliminated if Iran agrees to suspend its illegal enrichment activities."

Iranian President Mahmoud Ahmadinejad dismissed the new sanctions and said Iran didn't recognise them.

Iran's UN Ambassador Mohammad Khazaee said: "Iran as one of the most powerful and stable countries in the region has never bowed and will never bow to the hostile actions and pressures by these few powers and will continue to defend its rights," he said.

The resolution was approved by a vote of 12-2, with Lebanon abstaining and Brazil and Turkey voting "no."