Indian shares open flat, then turn negative

MUMBAI, Dec 17 (Reuters) - Indian shares opened 0.01 percent up on Monday and then quickly slipped into negative territory, led by Oil & Natural Gas Corp (ONGC.BO) and HDFC Bank (HDBK.BO). At 9:58 a.m. (0428 GMT), the 30-share BSE index .BSESN was down 0.38 percent, or 75.31 points, at 19,955.52, with 20 components falling.

The 50-issue NSE index was down 0.66 percent at 6,007.75. (Reporting by Devidutta Tripathy)