The All Share Price Index closed at 6,991.
06, down 1.39 percent (98.63 points), while the more liquid Milanka index fell 1.
38 percent (107.64) to close at 7,679.94, according to stock exchange provisional figures.
Turnover was almost four billion rupees.
The market is going through a "technical correction" after an overextended rally, said an analyst who did not wanted to be named.
The Colombo Stock Exchange nearing a 19-month bull-run last week overtook the Mongolian Index as the best performing index in the world.
Market watchdog, the Securities and Exchange Commission, said the post-war optimism was boosted further by unwarranted credit extended by brokering firms.
Nawaloka Hospitals controlled by the Dharmadasa family closed at 9.30 rupees, up 10 cents (1.1 percent) with 42.8 million shares traded. SMB Leasing closed at 2.00 rupees, down 10 cents (4.76 percent) on 6.8 million shares changing hands.
John Keells Holdings, an index heavy stock with business interests in transport, leisure, retail, food processing and financial services sectors, closed at 338.10 rupees, down 11.50 (3.29 percent).
Commercial Bank closed at 280.00 rupees, down 8.70 (3.0 percent), while Hatton National Bank closed at 408.
20 rupees, down 7.30 (1.76 percent).