The Sensex at the Bombay Stock Exchange gained 134 points or 0.8 per cent, to 16,844 in opening trade, on Thursday morning, on continued buying by investors, in line with firm Asian markets. But later the Sensex showed very high volatility, as it swung between negative and positive zones. After falling 164 points at one stage, the 30-share BSE index again rebounded, to stand a modest 48 points, or 0.3 percent in positive territory, at 16,758 in afternoon deals, a short while ago. Other regional markets in China, Japan, Singapore, South Korea, Taiwan and Hong Kong had logged gains of between 0.1 percent and 1.8 percent, on Thursday. Stocks rose after sentiment was boosted by assurances from France and Germany that Europe will stand behind Greece as that nation struggles to cut its debt burden. Over in the US, the Dow Jones Industrial Average had ended 1.3 per cent higher, overnight.