This came despite regional shares being generally optimistic over a free-trade deal being stuck between Britain and the EU, which alleviated concerns of trade disruptions caused by Brexit.
At 12.30pm, the benchmark index was down 4.96 points to 1,642.54, holding above a technical support of 1,640 pegged by some analysts.
Among the market heavyweights, Tenaga fell four sen to RM10.64, Hartalega was down 18 sen to RM12.54, Genting dropped nine sen toRM4.44 and Supermax slid 10 sen to RM6.82.
Meanwhile, Nestle rose 40 sen to RM138.88, KL Kepong added 22 sen to RM24.22 and Press Metal climbed nine sne to RM8.
Top actives were AT Systemization up 2.5 sen to 19 sen, M&G rising 12.5 sen to 20 sen and Iris gaining four sen to 42 sen.
Energy counters established a firmer footing after crude oil prices bounced higher on the Brexit deal and a drawdown in US inventories.
Brent crude was 49 cents higher to US$51.69 a barrel and WTI crude rose 40 cents to US$48.52 a barrel.
The Bursa Malaysia Energy Index was seen rising 0.3% to 887.15 amid cautious gains on the former prices.
Among the gainers, Hibiscus Petroleum rose 0.5 sen to 58.5 sen, Dayang gained two sen to RM1.17 and Scomi Energy added 1.5 sen to 10 sen.
In Asia, Japan was up 0.4% while China's benchmark index was down 0.2%, weighed down by news of an antitrust investigation against Alibaba Group. Hong Kong's Hang Seng however was 0.2% firmer.
South Korea's Kospi jumped 1.2% and Australia's ASX 200 was up 0.3%.