The Liberation Tigers of Tamil Ealam today observe "Black Tiger Day" to honour 261 suicide bombers who have carried out attacks since their first strike 19 years ago.
The already tight security in the capital Colombo was bolstered with the closure of several roads in front of key military and economic targets, police said as heavily armed soldiers took up positions at intersections.
Traders said the mood was subdued with some modest profit taking on mid sized stocks.
The benchmark All Share Price Index edged up 0.01 percent or 0.25 points to 2,113.40 on volumes of 19.7 million shares worth 213.74 million rupees.
Foreign interest in conglomerate John Keells Holdings helped lift its share price up 0.2 percent to 132.00 rupees.
The family controlled Hemas Holdings also attracted foreign interest which helped its share price advance 2.
0 percent to 103.00 rupees.
Elsewhere, dairy giant Nestles jumped 4.75 rupees to 185.25 rupees, while Ceylon Oxygen gained 0.4 percent to 225.00 rupees.
The liquid Milanka Price Index, which tracks 25 stocks, slipped 0.15 percent or 4.18 points to close at 2,722.56
On the foreign exchange market, the rupee ended a tad higher at 103.95 after closing at 104.00 against the greenback on Tuesday.
The extra security measures in the capital prompted some buying in the forward market, but overall volumes remained slim, dealers said.
The overnight call money ended unchanged at 11.00 percent, although the money market's liquidity deficit swelled to 920 million rupees on sustained borrowings and fund outflows.
The Central Bank sold 5.782 billion rupees worth of treasury bills at the auction today with 3-month paper climbing 6-basis points to 10.
22 percent.
Yields for 6-month treasuries gained 1-basis point to 10.45 percent, while one-year notes edged up by the same to 10.46 percent.
The bank bought 3,263 million rupees worth of paper for its own stock.