Banking giant Standard Chartered on Tuesday rejected a US regulator\'s claim that it hid $250 billion in transactions with Iranian banks in violation of US sanctions. The denial came a day after the New York\'s Department of Financial Services (DFS) threatened to revoke the bank\'s licence and imposed fines, as the regulator branded the London-based lender as a \"rogue bank\". \"The group strongly rejects the position or the portrayal of facts as set out in the order issued by the DFS,\" group company secretary Annemarie Durbin said in a statement. \"The group does not believe the order issued by the DFS presents a full and accurate picture of the facts.\" The US regulator accused Standard Chartered of systematically disguising foreign exchange deals with Iran in a breach of controls that potentially opened up the US banking system to terrorists and criminals. It has ordered the bank to explain the alleged violations on August 15, in the latest US move against foreign banks accused of failing to prevent money laundering and other illicit transactions. \"The group takes its responsibilities very seriously, and seeks to comply at all times with the relevant laws and regulations,\" Durbin said, adding that it had \"engaged with the US agencies\". The bank\'s Hong Kong-listed shares plunged 7.5 percent to HK$174.0 when the market opened following the news late Monday from the United States. The regulator\'s move came after a US Senate report last month accused HSBC, also based in London, of concealing more than $16 billion in sensitive transactions with Iran and Mexican drug lords from 2001 to 2007.