Detectives have arrested four people over a £1m cyber-theft from two banks using computer viruses embedded in emails.
The plot is believed to have been carried out by a suspected international crime ring and police seized £80,000 and a live grenade during raids were carried out in the Enfield and Islington areas today.
Bank customers were targeted with fake emails, which appeared to be legitimate emails from the banks but in fact carried malware that allowed the gang to take a total of £1m from the customers' accounts.
Police seized the cash, jewellery and a Range Rover during the raids, and bomb disposal experts were called to deal with the grenade, which was discovered at a property in Bowes Road, Enfield.
Detective Chief Inspector Jason Tunn, from Scotland Yard's cybercrime unit, said: "These arrests follow an investigation into what we suspect is an international and organised crime targeting a number of bank customers in London and across the UK.
"The victims have been hoodwinked by malware-carrying emails purporting to be from their banks, and subsequently had money taken from their accounts."
Two men, both aged 31, and two women, aged 24 and 27, were arrested on suspicion of conspiracy to defraud, conspiracy to launder money, and possession of an explosive.
The men are currently being questioned at a police station in central London, while the women have been released on bail until early next year.