DEPENDING on how oil prices behaved, traders alternated between heavy doses of short-selling and short-covering this week, resulting in the Straits Times Index recording large swings throughout the five days.

On Friday, the index rounded off a volatile week with its most sedate session in weeks, ending just 0.7 of a point lower at 2,656.87, bringing its gain for the week to 117 points or 4.6 per cent.

Banks and Singtel have been the index's main propellants as well as depressors, the excuse to short-sell coming from concerns over their exposure to a collapsing oil sector, the trigger for short-covering from arguments such as "valuations are attractive" and "concerns are overstated".

During the week, UOB and OCBC released their results, which were largely within expectations. As one observer said, "at least there were no shocks".

Elsewhere in the market, SembCorp Marine enjoyed strong support, was queried by the Singapore Exchange and replied that other than market speculation of a privatisation, it did not know of reasons for the play on its shares. On Friday, the stock ended unchanged at S$1.70 on volume of 3.9 million, for the week it gained S$0.28 or almost 20 per cent.

In the telco sector, news on Thursday that a fourth player may be allowed brought some pressure to bear on the three existing parties on Friday, though this eased off as the session progressed. StarHub and Singtel closed S$0.03 weaker at S$3.46 and S$3.70 respectively, while M1 added S$0.02 at S$2.54.