A suspected blackmailer believed to have sent two letter bombs which exploded at offices in the Netherlands on Wednesday has demanded payment in bitcoins, Dutch police said. No one was hurt in the blasts in the mailroom of an ABN AMRO bank office in Amsterdam and an office of the Japanese copier firm Ricoh in the eastern town of Kerkrade, near the German border. "Payment of bitcoins is required in the extortion letter" sent with the bombs, Dutch police said in a statement, referring to the virtual currency.