THE property sector intensified its downward momentum yesterday, with the index constituent property counters plunging 7.94 per cent to considerably underperform the overall market. The Hang Seng Index dived 536.22 points or 5.01 per cent to 10,176.51, on an improved turnover of $9.24 billion. The Hang Seng property sub-index tumbled 1,480.72 points to 18,637.01, exerting overwhelming pressure on the market. Commercial and industrial stocks also fared badly, sliding 5.74 per cent or 418.54 points to 7,286.07. The other two sectors, which outperformed the main index, also shed more than three per cent each. Finance tumbled 3.24 per cent or 298.62 points to 9,211.18, while utilities went down 3.08 per cent or 346.94 points to 11,247.5. Yesterday's market went on a roller-coaster ride. The index opened at 10,651.07 - about 60 points below Wednesday's close of 10,712.73 - which was the day's highest level. It swiftly fell to 10,472.48 in 15 minutes before it found support to bounce back to 10,625.41 at 11 am. Sellers made a quick return, which promptly brought out bargain-hunters. The last 15 minutes of morning trading was dominated by sellers, driving the index to its lunch close of 10,355.68. The afternoon saw further frantic selling in the trading hall, resulting in the index sinking to the day's low of 10,162.2 points at 2.45 pm. Buying interest then lifted the index to the 10,300 level shortly after 3 pm, before it skidded to the day's close. The All Ordinaries Index slumped 4.91 per cent, suggesting selling pressure was also considerable in second and third liners. January index futures lost 445 points to 10,340, giving a 163.49-point premium to the spot market. In the morning, they were trading at a discount of about 50 points to the spot market until shortly before noon, briefly losing its premium position and before recovering just towards the lunch close. The afternoon saw them trading at a consistent premium of up to 150 points. About 21,801 January contracts were traded, compared with a total market activity of 22,407. ''The options market was again active. Many traders sold the 102 puts in both February and June, as they feel that the market was coming to a short-term low and the high premium gave sufficient downside protection,'' said Jardine Fleming Futures head of derivatives research Virginia Mumford. ''Call buyers were also active even though the volatilities climbed higher,'' she added. Among the index constituent stocks, Hang Lung Development was the biggest loser, plummeting 11.57 per cent or $2.20 to $16.80, on a turnover of $142.59 million. Bank of East Asia saw no more sign of its strength in the past days as it dipped 6.78 per cent or $4 to $55 on the day's second heaviest turnover of $480.31 million. Peregrine Derivatives yesterday launched a covered warrant issue on the counter. Chevalier (OA) International continued its upward trend to become the second biggest gainer in percentage terms, rising 12.58 per cent or 18 cents to $1.61 on the day's second heaviest trading volume of 77.16 million shares worth of $120.43 million. Southeast Asia Properties was the day's sixth biggest gainer on news of a 654 per cent surge in interim profit for the six months to September 30 last year. The stock moved up four per cent or 20 cents to $5.20 on a turnover of $741,500. HSBC was the most active counter in turnover terms, but it fell $3 to $103 as shares worth $787.75 million changed hands. Hutchison Whampoa had the third highest turnover of $441.72 million on the back of a $1.75 drop to $31. Great Wall Electronic on Wednesday bought back 370,000 ordinary shares at prices ranging between $1.35 and $1.38 a share.