Mumbai: After roller-coaster trade, the BSE benchmark Sensex on Wednesday ended flat -- a marginal slip of 16 points, as investors turned cautious on renewed concerns over the euro-zone crisis and a weak global trend.

The Sensex, which lost 324 points in the last two trading sessions, shuttled between 17,615.92 and 17,337.65 before ending with a loss of 15.98 points at 17,464.85.

Auto and financial stocks led the declines.

However, the broad-based National Stock Exchange index Nifty managed to settle with a small gain of 0.50 point at 5,258.45 as most-weighted Reliance Industries made gains.

Before this, the index moved between 5,300.10 and 5,204.95.

Brokers said investor worries resurfaced over the euro-zone debt crisis, after Greece's called for a referendum on a plan by European leaders to defuse the crisis.

They said auto sector index suffered heavy losses amid slow growth because of high interest rates and a possibility of further hike in fuel prices.

Weak openings in Asia and Europe pushed investors away.

Sensex has tumbled more than 14 percent this year, on account of the high interest rate regime to tame inflation and slow economic growth.

Fifteen of the 30-BSE index stocks closed in the red, while others gained.

The auto sector index suffered the most by losing 0.44 percent to 9,248.68.

Gains by heavy-weight Reliance Industries, up 1.27 percent.