UPDATE 1 — UK police arrest three suspected of involvement in insider dealing ring

(Adds FCA quote, paragraph 3-4, details from paragraph 5) LONDON, Oct 13 (Reuters) — Three people have been arrested in Britain on suspicion of being involved in a criminal insider dealing and money laundering plot, the Financial Conduct Authority said on Tuesday. More than 100 staff and officers searched five residential premises in London and the northern English city of Manchester in a joint operation with the National Crime Agency, seizing more than 30 mobile phones, laptops and tablets, the FCA said. "Insider dealing is a serious threat to the integrity of our markets," the FCA's joint enforcement head, Steve Smart, said in a statement. "Working with partners, we will continue to use all the powers at our disposal to crack down on serious and organised crime groups engaged in market abuse." The FCA, which said it could not comment further at this stage, secured four insider dealing convictions last financial year, with two resulting in record, combined prison sentences of 11 years. The regulator has stepped up enforcement action on suspected insider dealing, with recent cases involving an oil rig consultant, traders and a financial adviser. (Reporting by Kirstin Ridley, Editin