Singapore shares closed 0.05 percent lower on Monday, as investor sentiment was hurt by continued uncertainty over the U.S. government shutdown and the upcoming debt ceiling debate. Investors fretted over how long the U.S. government will remain shut down. Furthermore, there was caution over the upcoming debate in the U.S. over the debt ceiling. On Sunday, House Speaker John Boehner would not bring up bills to fully reopen the government or increase the borrowing limit unless the Democrats agree to broader talks aimed at cutting the deficit. Nevertheless, some of the researchers said they saw downside risks somehow limited at the moment. \"We believe further downside should be limited at around 3,100 points and see bargain hunting opportunities there or slightly above on the presumption that the US does not sink into debt default,\" DBS Group Research said. CIMB Research said \"closing sharply below the 3,120 points and 3,154 points gap would likely signal that there is more downside to come, probably targeting the 2,990 low once more.\" The benchmark Straits Times Index dropped 1.49 points, or 0.05 percent, to close at 3,136.59. Trading volume was 4.07 billion shares worth 1.03 billion Singapore dollars (824 million U.S. dollars). Decliners outnumbered advancers 401 to 106, while 451 stocks closed unchanged. Among top actives, Blumont Group, Asiasons Capital and LionGold Corporation plunged 85.2 percent, 85.5 percent and 71.4 percent to 13 Singapore cents, 15 Singapore cents and 25 Singapore cents respectively. Singapore Exchange barred short selling and margin trading of the three stocks that were suspended after sharp plunges last Friday, declaring them \"designated securities\" subject to stricter rules and added scrutiny. KS Energy sank 14.6 percent to close at 52.5 Singapore cents. It announced its move into Mexico with the signing of a Memorandum of Agreement with one of Mexico\'s renowned conglomerate Empresas ICA. A jointly controlled entity will be formed to tap into Mexico \'s expanding oil and gas industry by providing drilling services and heavy capital equipment for the offshore oil and gas exploration market. Among the top gainers, Jardine Matheson rose 0.4 percent to close at 54.13 U.S. dollars, while Jardine Cycle and Carriage became one of the top losers by dropping 1.5 percent to 34.10 Singapore dollars. (1 U.S. dollar equals to 1.25 Singapore dollars)