At 12.30pm, the key index was down 16.37 points to 1,572.68.
"Overall, the key market bellwether remains suscceptible to persistent selling pressure after previously crossing below the 25-day SMA while its further progress is expected to be blocked by a descending trendline," said Kenanga Research in its technical outlook.
However, it said the presence of buying support on weaness may cushion the downside.
Over the coming sessions, the research house expects the FBM KLCI to gyrate between its first support and resistance thresholds of 1,550 and 1,600 points.
There was broad-based selling pressure on the market, led lower by blue chips including Tenaga Nasional down 38 sen to RM10.06, Press Metal sliding 12 sen to RM4.78, Sime Darby Plantation dropping 21 sen to RM4.19 and IHH Healthcare shedding 15 sen to RM5.71.
Top actives were Vsolar down 0.5 sen ot 1.5 sen, Itronic up five sen to 29 sen and Focus unchanged at four sen.
Asian markets were also in the red as investors withdrew from equities following the US central bank's shift in monetary policy.
Japan's Nikkei slumped 3.6% while South Korea's Kospi fell 1.1%.
China's main index dropped 0.2% and Hong Kong's Hang Seng lost 1.3%.
Australia's ASX200 was down 1.9%.