BARGAIN hunting and strong technical support triggered a 125.43-point bounce in the Hang Seng Index to 5,980.04 yesterday amid frenetic activity. Turnover was $3.89 billion, down $1.34 billion on Monday's $5.23 billion figure. Some dealers spoke of their surprise at the strength of the rebound in highly volatile trading, from a support level for the index at 5,850, in the wake of a new fracture in Sino-British relations. Share dealers will remain on tenterhooks today, however, on the words of Mr Lu Ping, the director of the Chinese State Council's Hongkong and Macau Affairs Office. He is due to appear at a press conference at 3 pm with regard to the current state of the Sino-British democracy row. The gazetting of Governor Chris Patten's democracy proposals for Hongkong on Friday afternoon wiped more than than $131 billion off market capitalisation. Selling sent the index down eight per cent in two days and 10 per cent since the 6,508 record high of last Wednesday. Yesterday, the index swung through a tight 80-point range, indicating that part of the rally was due to overnight trading in London before the market opened. The re-rating of HSBC Holdings played a special part in the overnight index bounce as it opened yesterday morning significantly higher than the $64.50 closed in Hongkong on Monday evening. HSBC announced a 94 per cent rise in pre-tax profits in sterling to GBP1.7 billion and a 68 per cent rise in Hongkong dollar net profit to $14.32 billion, for the year ending December 31, 1992, well ahead of market expectations. At the opening of trading in Hongkong, pent-up bargain hunting caused a 70-point jump in the index and an attempt to break through 5,980. The index was to challenge 5,980 twice more during the day, but buying momentum failed to push it through. Reports from China that Beijing was due to ban all UK-linked investment following the gazetting of the democracy proposal caused nervousness towards the end of the morning session, leaving the index at 5,941.52 at the lunch-time close. PBI Securities sales director Andrew To Koon-hung said: ''The rebound was to be expected as the fall in the index since Friday placed the market in an oversold position and technical buying was inevitable. ''Much now depends on politics and Sino-British relations as far as index movement [volatility] and direction is concerned.'' Index futures recorded a turnover of 8,884 contracts, well down on Monday's 15,371 figure. The March contract remains at a deep discount of 117 points at 5,863. The June contract looks worse at 5,855 on a turnover of 539 contracts. Property stocks fared best in the rise, with the sub-index up 2.44 per cent to 9,194.37, having fallen 6.03 per cent on Monday. A significant factor in the rebound was Cheung Kong, the third most heavily traded stock and the third biggest index mover of the day. The Li Ka-shing flagship stock rose 80 cents on $193.74 million of turnover. Trading has been heavier than usual in anticipation of the group results for 1992, due to be announced tomorrow. Finance stocks were the second best performers on the day, with the sub-index up 2.2 per cent to 6,059.56, having plummeted 3.62 per cent on Monday. HSBC Holdings on its own accounted for 14 per cent of total market turnover and 14 points on the index. It rose $1 to $65.50 on $543.43 million turnover. Including Hang Seng Bank and their respective covered warrants, HSBC-associated securities made up more than 25 per cent of total market turnover. Hang Seng Bank rose $2.50 to $65 on $264.3 million of turnover. Taken together the two banks accounted for 36.65 points or 30 per cent of the day's move in the index, according to Bloomberg data. Utilities rose 1.55 per cent to 7,020.93, and commerce and industry rose 2.3 per cent to 4,322.66.