Indian equity markets opened sharply higher on Wednesday, with the benchmark indices gaining nearly 1 per cent each as investors awaited the US Federal Reserve's policy decision.

Sensex opened at 77,423.77, up 657.85 points or 0.86 per cent, while the Nifty started at 24,176.65, rising 191.30 points or 0.80 per cent.

Sector-wise, most indices traded in the green in early deals, led by Nifty IT which jumped over 2 per cent.

Meanwhile, Nifty MidSmall IT & Telecom gained 1 per cent, followed by Nifty Chemicals (0.99 per cent) and Nifty FMCG (0.81 per cent).

On the downside, Nifty Realty fell 0.39 per cent, while Nifty Oil & Gas slipped 0.15 per cent.

Analysts said global markets remained mixed ahead of the Fed's policy decision and key corporate earnings, while higher Brent crude prices amid renewed geopolitical tensions could keep commodity prices volatile.

They said the market's current range-bound trend is likely to break on the upside, supported by fairly valued Nifty stocks, though sustained FII buying would depend on greater clarity over crude oil prices and the progress of the monsoon.

The Fed is widely expected to keep rates unchanged, a move that is already priced into Indian markets and is therefore unlikely to trigger a significant reaction, analysts added.

Additionally, Brent crude rose 4.85 per cent to $88.17 per barrel, while US WTI crude gained 5 per cent to $83.30 per barrel.

Asian markets traded mixed, with Japan's Nikkei down 2 per cent, Hong Kong's Hang Seng up over 1 per cent and South Korea's KOSPI falling nearly 9 per cent.

Wall Street ended mixed overnight, with S&P 500 gaining 0.21 per cent while the Nasdaq slipped 0.22 per cent.