SINGAPORE - Singapore shares posted their sharpest fall in 18 months on Tuesday as the crash in oil prices showed no signs of turning around.

The benchmark Straits Times Index (STI) tumbled 2.4 per cent or 79.05 points to 3,215.09.

This was the biggest daily percentage drop since June 2013, according to data from Bloomberg.

All but three of the 30 blue-chip stocks that make up the STI fell. The three that rose eked out only slight gains.

Rigbuilders continued to languish but the index was largely dragged down by banks and commodity firms on Tuesday.

Another culprit was casino operator Genting Singapore, which slid 5.1 per cent or 5.5 cents to $1.03 with 36.7 million shares traded.

Across the overall market, about 1.2 billion shares worth $1.37 billion changed hands.

Losers far outnumbered gainers at 310 to 88 counters.