Interbank rates staged modest rises yesterday amid fears about the impact of further falls in regional currencies. Traders saw no significant speculative pressure developing against the Hong Kong dollar. One-month interbank lending rates - with which banks finance most of their long-term assets - rose 1.5 percentage points to close at 8.5 per cent. The benchmark three-month rate - the base on which most corporate debt is set - jumped 1.375 percentage points to 10.5 per cent. Interbank lending rates for shorter maturities, except the overnight rate, all closed higher than US interest rates, up from their previous discount levels, indicating banks were wary of volatility in short-term rates in the face of a deteriorating regional situation. The 'Tom-next' rate - overnight funds lent today and repaid tomorrow but with the rate determined yesterday - surged to 5.75 per cent, while the one-week rate stood at 7 per cent. Overnight rates remained soft at 4.5 per cent but still 0.25 percentage points higher than last week's 4.25 per cent. The Hong Kong dollar spot exchange rate remained stable at $7.75 per to the US unit. Traders believed the Hong Kong Monetary Authority had been intervening heavily both in the spot market as well as the interbank market, lending three-month funds at 10 per cent. Standard Chartered Bank forex and money markets manager Stephen Yau Chin-fai said yesterday's rise in interbank rates was mostly driven by activities in the Hong Kong dollar forward market, which saw a higher-than-normal level of overseas orders. He said it was difficult to determine if these orders were from speculators or backed by real commercial demand. As total volume remained thin and spread stayed wide, market movements could have been exaggerated. Citibank money markets manager Chordio Chan said banks were cautious in such an environment and tried to remain as liquid as possible, pushing rates up further.