The Bombay Stock Exchange benchmark Sensex on Friday gained over 204 points in opening trade. The sensex was trading at 16844, up by over 178 points when reports last came in. Similarly, the wide-based National Stock Exchange index Nifty alsorose by 50 points to 5,053 points. Stockbrokers said the trading sentiment remained firm on the back of a rebound in global markets and China's assurance that Europe remains a key investment market for its foreign exchange reserves. The US Dow Jones Industrial Average ended 2.85 per cent higher in the previous session. I(n Asian markets, Japan's Nikkei gained 1.51 per cent and Hong Kong's Hang Seng were up 1.96 per cent in morning trade on Friday.