Continuing its slide for the fourth straight session, the Sensex at the Bombay Stock Exchange shed as much as 273 points, or 1.4 percent, to slip below the 20,000 point level, at 19,912, in afternoon trade, today. Earlier, in the morning, the Sensex had opened 57 points lower, on concerns over a likely interest rate hike by the central bank, later this month, and weakness in other Asian bourses.The Sensex has already lost 375 points in the last three trading sessions.Other Asian markets in Indonesia, Hong Kong, Singapore and Taiwan were down by between 0.2 percent and 2 percent, today, on investor caution ahead of US non-farm payrolls data. Over on Wall Street, the Dow Jones Industrial Average had lost 0.2 percent, overnight.