Iran's President Hassan Rouhani said on Wednesday Britain would face "consequences" over the seizure of an Iranian oil tanker. He also said Iran's increase in uranium enrichment was for peaceful aims, the semi-official news agency Tasnim reported. Iran has demanded the immediate release of the tanker Grace 1, which British Royal Marines boarded off the coast of Gibraltar last week and seized over accusations it was breaking sanctions by taking oil to Syria. "You [Britain] are the initiator of insecurity and you will realise the consequences later," Rouhani was quoted by Tasnim as saying after a cabinet meeting. Rouhani also said Iran's decision to increase uranium enrichment would produce fuel for power plants and serve other peaceful aims, and that it was within the framework of Iran's 2015 nuclear deal with world powers.  It comes as Britain deployed Royal Navy warship HMS Montrose into the Strait of Hormuz to protect UK shipping after Iran threatened to seize them in revenge. She is believed escorted oil tanker Pacific Voyager as she sailed through the piece of sea that separates the United Arab Emirates from Iran. The tanker had to be checked on by UK officials over the weekend as she stopped close to Iranian waters. The waterway has been the scene of five attacks of tankers this year amid a renewed flaring of tensions in the Gulf.    Iran has been squaring up to the West as it reels over the scrapping of the so-called nuclear deal by the US, which traded a pledge not to develop nukes for eased sanctions. The ayatollah has been demanding that nations such as Britain and its European allies pick-up the slack as Donald Trump’s administration imposes crushing new penalties. Britain however infuriated Iran last week when the Royal Marines seized the Grace 1 supertanker as she entered the Mediterranean. Commandos took the vessel without a shot being fired as it is suspected of breaching EU sanctions on the brutal Syrian regime of Bashar al-Assad.    Iran responded by threatening to seize British ships in retaliation amid fears of a new tanker war in the Gulf.  Five oil tankers and a cargo ship have been attacked in the Gulf in the past two months. Tehran denies any involvement in the attacks, but they have been blamed by the US.  And in an escalation, Iran shot down a US drone – nearly prompting a limited strike by Washington before an 11th hour U-turn by Trump.     Iran has since broken its nuclear agreement by stepping up its enrichment of uranium. Tehran has said the measures are just for power plant fuel, and will not be used for the development of nukes. The foreign ministers of Britain, France and Germany, plus the foreign affairs chief of the European Union, said in a statement that Iran was "pursuing activities inconsistent with its commitments”. Trump’s administration argues the deal was too soft on Iran and it didn’t impact its missile programme of sponsor of terrorism.