RE-EXPORTS surged 24.8 per cent in the first quarter as Hongkong continued to push manufacturing and production across the border. While the healthy rates are keeping the local economy buoyant - accounting for 4.5 per cent of GDP at an annual rate, according to one estimate - economists warn that rising reliance on China makes Hongkong increasingly vulnerable to external actions aimed at the mainland. Government figures show that re-exports now make up 78 per cent of total exports, compared with 74 per cent over the same period last year. Hongkong Bank senior economist Chan Kwok-kei said: ''Because of the increased dependence on re-export trade, any interaction with that flow, be it MFN or unexpected matters, of course will affect Hongkong.'' But he added that within four years the notion of re-exports would be broadly wiped out as Hongkong reverted to China. The integration of the two economies was already under way, he said. Provisional figures released by the Census and Statistics Department yesterday show that domestic exports barely changed over the first quarter of last year at $48.71 billion. Imports, pushed up strongly with re-exports, rose 17.7 per cent to $233.05 billion. Total exports were up 18.4 per cent to $222.91 billion. The visible trade deficit for the quarter stands at $10.15 billion, $509 million higher than that recorded over the same period last year. Smith New Court regional economist Geoff Lewis reckoned that flat domestic exports - now largely dependent on broadly stable demand from the Asian countries - could be spiked up towards the latter half of the year as economies in the industrialised countries recovered. He was also not concerned about the rising trade deficit, which has caused anxiety in certain quarters. He said: ''The figures are not that distressing, and not much greater than 1992. ''I don't think it is much of a problem at these levels, because the invisible balance has been improving substantially, offsetting some of the deterioration in the trade account.'' On a monthly basis, re-exports last month rose 23.9 per cent to $63.47 billion and domestic exports reversed the February decline to perk up 1.7 per cent. Taken together, total exports grew 18.4 per cent to $80.81 billion. Hongkong demand for foreign goods remained strong in March, with imports picking up 17.6 per cent to $86.85 billion. Nomura Research Institute economist Daryl Ho Hon-kit said: ''It is a very clear picture: exports in the first quarter of this year are quite stable, and I would expect this 18.4 per cent growth is largely driven by the China market. ''In the first two months of the year, total exports to China grew by 39.2 per cent. It is an important driving force for the total exports of Hongkong.'' Detailed breakdowns of the figures showing which countries are buying what goods are due to be released by the Government early next month.