South Korea's mutual financing firms saw their deposits increase 3.9 percent last year from a year earlier, but the pace slowed down amid concerns over their deteriorating asset quality and stricter supervision, the financial watchdog said Thursday. The combined outstanding amount of deposits at four mutual financing companies, including Nonghyup, or the National Agricultural Cooperative Federation, stood at 302.9 trillion won (US$283 billion) at the end of December, up 11.4 trillion won from 291.5 trillion won at the end of 2012, according to the Financial Supervisory Service (FSS).