* Foreign investors buy blue chips
* Foreign investors net buyers for 10th session
* Rupee weaker on importer dlr demand
COLOMBO, Feb 23 (Reuters) - Sri Lanka's stock market surged more than 2 percent in high turnover on Thursday on foreign buying in Aitken Spence PLC and other large blue chip purchases, while the rupee fell on importer dollar demand.
The main share index rose 2.14 percent in early trade, but ended 1.6 percent or 86.63 points firmer at 5,507.60, highest since Feb. 8. It has risen 9.93 percent over the last six sessions from an 18-month low, once shares dropped into oversold territory.
"The buying pressure is there as the investors were taking advantage of the low level of the market," said Sarath Rajapaksa, head of research at Capital Trust Securities in Colombo.
The index rose higher in neutral territory on Thursday with the 14-day Relative Strength Index at 49.346 from Wednesday's 44.775, Reuters data showed.
The Colombo bourse is one of the worst performers this year among Asian market, with a 9.33 percent loss while the majority of others have had positive returns.
Foreign investors were net buyers of shares worth 530 million Sri Lanka rupees ($4.46 million) on Thursday, extending the net foreign inflow to 2.81 billion rupees so far this year, after net outflows of 19.1 billion last year.
Aitken Spence PLC, which saw foreign buying of 4.4 million shares on Thursday, fell 0.43 percent to 115 rupees.
Market Heavy weight conglomerate John Keells Holdings PLC rose 1.90 percent to 177.20 rupees a share.
The day's turnover was 3.71 billion rupees, highest since Dec. 1. Last year's average turnover was 2.3 billion. The day's volume was 88.2 million shares, compared to last year's record daily average of 102.7 million.
The rupee closed weaker at 119.30/45 a dollar, compared with Wednesday's close of 118.80/85 on heavy importer dollar demand. It hit an all-time low of 120.90 on Feb. 15, after the central bank stopped supporting a specific price level. ($1 = 118.7500 Sri Lanka rupees) (Reporting by Ranga Sirilal and Shihar Aneez; Editing by Bryson Hull)