The Bombay Stock Exchange benchmark Sensex today recovered by over 87 points to open at 19,959 in the morning trade. Later it consolidated its gains and crossed 20 K mark to quote at 20,019, up by 146 points a short while ago. Analysts said the gain in sensex is due to fresh buying by funds and retail investors amid a firming trend overseas.Meanwhile, in Asian markets, the Hong Kong's Hang Seng Index was up by 0.68 per cent, while Japanese Nikkei gained 0.66 per cent in the morning trade today.In the US, the Dow Jones Industrial Index ended 1.18 per cent up yesterday.