Mumbai, Apr 4 (IANS): Key Indian equity indices tumbled during the late-afternoon session on Wednesday to provisionally close on a lower note after further trade protectionist measures were imposed on each other by two major global economies.

Besides, investors remained cautious ahead of the outcome of the central bank's first bi-monthly monetary policy of 2018-19 on Thursday.

Market observers said that except for S&P BSE auto index, all the other indices slumped.

The barometer 30-scrip Sensitive index (Sensex) of the BSE shed almost 500 points from its day's high at 33,505.53 points to provisionally close the day's trade at 33,019.07 points.

On a session-wise basis, the BSE Sensex at 3.30 p.m. closed lower by 351.56 points or 1.05 per cent to 33,019.07 points from its previous session's close.

On the National Stock Exchange (NSE), the wider Nifty50 declined by 116.60 points or 1.14 per cent to close at 10,128.40 points.

According to market observers, the domestic equity markets reacted to intensifying trade war fears after China on Wednesday unveiled a list of products worth $50 billion imported from the US that will be subject to higher tariffs, including soybeans, cars and chemical goods.

The Customs Tariff Commission of the State Council decided to impose additional tariff of 25 per cent on 106 items of products under 14 categories as a countermeasure after the US administration published a list of about 1,300 Chinese products it plans to hit with a 25 per cent tariff.

On Tuesday, the equity indices closed with appreciable gains -- despite volatility in the global markets -- led by healthy buying in banking, auto, oil and gas, and healthcare stocks.

The Nifty50 edged higher by 33.20 points or 0.33 per cent to close at 10,245 points, while the Sensex closed at 33,370.63 points -- up 115.27 points or 0.35 per cent from its previous session's close.