HONG KONG/SHANGHAI (REUTERS) - China's onshore yuan firmed against the US dollar on Tuesday (Jan 5) after suspected interventions from the central bank, three traders told Reuters.

"It's quite obvious that the central bank has intervened in the market via big Chinese banks in the morning and trading was very active," said a trader at a Chinese bank in Shanghai.

The yuan closed at 6.5338 per US dollar on Monday, but strengthened immediately after the opening on Tuesday and traded at 6.5197 by mid-morning.

China's forex and stock markets had plunged sharply on Monday in response to weak economic data, sparking a global sell-off of riskier assets.

In the offshore yuan market, where the central bank usually takes a hands-off attitude, the yuan remains weak and hit 6.6446 in early trade, the lowest level in more than four years.