The Sensex and Nifty were trading down by nearly 0.3 per cent as Asian stocks fell after the United States launched cruise missiles against an air base in Syria, raising the risk of confrontation with Syrian backers Russia and Iran.

US President Donald Trump has ordered the strikes against a Syrian air base controlled by President Bashar al-Assad's forces in response to a deadly chemical attack in a rebel-held area, a US official said.

Facing his biggest foreign policy crisis since taking office in January, Trump took the toughest direct US action yet in Syria's six-year-old civil war.

At 11.30 a.m., the 30-share BSE index Sensex was down 104.36 points or 0.35 per cent at 29,822.98 and the 50-share NSE index Nifty was down 26.1 points or 0.28 per cent at 9,235.85.

Among BSE sectoral indices, healthcare index fell the most by 0.65 per cent, followed by consumer durables 0.31 per cent, FMCG 0.27 per cent and banking 0.25 per cent. On the other hand, capital goods index was the star-performer and was up 1.00 per cent, followed by oil & gas 0.64 per cent, realty 0.56 per cent and PSU 0.26 per cent.

Top five Sensex gainers were Bharti Airtel (+2.17%), L&T (+1.86%), Bajaj Auto (+1.11%), GAIL (+0.79%) and Hero MotoCorp (+0.61%), while the major losers were Sun Pharma (-2.19%), Dr Reddy's (-1.3%), Coal India (-1.27%), HUL (-1.19%) and Reliance (-1.17%).

MSCI's broadest index of Asia-Pacific shares outside Japan shed 0.7 per cent in short order, and S&P 500 futures lost 0.5 per cent in an unusually sharp move for Asian hours. Japan's Nikkei was stripped of its early gains to slip 0.1 per cent.

Wall Street's major indexes had closed slightly higher on Thursday but finished well off session highs as investors were nervous about upcoming talks between China's President Xi Jinping and US President Donald Trump.

The Dow Jones Industrial Average closed up 14.8 points, or 0.07 per cent, to close at 20,662.95, the S&P 500 gained 4.54 points, or 0.19 per cent, to 2,357.49 after reaching a session high of 2364.16 earlier in the day.

The Nasdaq Composite added 14.47 points, or 0.25 per cent, to 5,878.95.