A DIRECTOR of Hongkong Land Holdings, Alasdair Morrison, says none of the group's prime office buildings in Central are on the market. His announcement was aimed at ending a spate of rumours claiming the company had been discussing the sale of Exchange Square III and other properties in its strong Central office portfolio. Among the other properties the Chinese press said might be sold were Swire House, Prince's Building and the Hongkong Club Building. The rumours were said by brokers to be the main reason for Hongkong Land's share price climbing over the past two days. Its share price rose 70 cents or 4.35 per cent to $16.80 yesterday, making the stock the largest percentage gainer of the 33 Hang Seng Index companies. Speaking after Hongkong Land's annual meeting yesterday, Mr Morrison said: ''We have none of our properties on the market. ''As a matter of policy we do not comment on market rumours.'' Hongkong Land's substantial Central office and retail property portfolio makes it the most formidable landlord in Hongkong's core business district. However, while office rentals in Central are rising, Mr Morrison said he expected the company's property earnings to remain flat this year. He blamed this on the phasing of the company's current three-year rent review cycle, which means it is this year putting up its rentals from a lower base. Mr Morrison said: ''Rents peaked in early 1989, so we are now reviewing what we previously reviewed in early 1990, which, although it was off the peak, was still quite high. ''We are still experiencing negative reversions in our reviews and renewals but we expect that to move into positive territory as we move into 1994. ''The longer term prospects for the commercial property market look very good.'' Group chairman Simon Keswick said in the company's annual report: ''The Hongkong commercial property market continues to show its resilience, with rising rents and firm capital values, and the investment initiatives taken during the year should enhance growth over the longer term.'' The occupancy rate for Hongkong Land's portfolio at the end of last year was an impressive 97.5 per cent, which has since improved.