After rising to a high of 1,457.64, the bourse succumbed to profit-taking to enter the midday break nearly one point lower at 1,450.75.
Trading volume was 3.72 billion shares valued at RM2.46bil, which put it on a par with the trading activity recorded at this time in recent days.
Global markets have been on a US-led rally as hopes over a global economic recovery took flight amid easing lockdowns and reports of early success in vaccine trials.
However, the political unrest in Hong Kong sparked by demonstrators against Beijing's move to clamp down on dissenters via a new security law put a lid on the optimism.
Following reports that hundreds were arrested in yesterday's protest rally, Hong Kong's Hang Seng Index slid 1.8% as the city's equities market proved unable to participate in the global rally.
Shanghai's Composite Index was also subdued, sliding 0.35% for a second day of losses as the political situation courted growing criticism from the international community.
Elswhere, results were mixed as Japan's Nikkei tracked Wall Street's performance to advance 1.1% while South Korea's Kospi was down 1.1%.
In Southeast Asia, key markets were also mixed with Singapore's Straits Times and Thailand's Stock Exchange joining the FBM KLCI slightly in the red even as Jakarta's benchmark jumped 1.9% and the Philippines Exchange rose 0.8%.
The FBM KLCI was seeing a broad-based retreat With 17 of the 30 stocks in the red, nine advancing and four unchanged.
Top Glove experienced fell 12 sen to RM12.74 after a surge in its share price previously, while Hartalega extended its gains by 16 sen to RM11.04.
Helping to offset losses on the index were Petronas Chemicals, which rose 22 sen to RM6.27 and CIMB, which added four sen to RM3.46.
On the actives list, Lambo rose 0.5 sen to 2.5 sen, Key Alliance lost one sen to 7.5 sen and Sanichi added 0.5 sen to 9.5 sen.
Oil prices descended amid a surprise build-up in US inventories, which dampened the demand outlook. US crude shed US$1.24 to US$31.57 a barrel and Brent dropped 86 cents to US$33.88 a barrel.
In currencies, the ringgit fell in tandem with the weaker oil prices. It lost 0.2% against the US dollar at 4.3550, 0.2% against the pound serling at 5.3362 and 0.1% agains tthe Singapore dollar at 3.0637.
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