The Sensex at the Bombay Stock Exchange opened 87 points, 0.5 per cent lower at 16,858, amid weak Asian markets, today. But the Sensex was later dragged down further by a weak opening in the European markets, and stood 274 points, or 1.6 per cent in the red, at 16,670, a short while ago. Other Asian bourses also lost ground, with key stock indices in Japan, China, Hong Kong, South Korea, Indonesia, and Taiwan down by between 0.3 per cent and 1.5 per cent after Chinese manufacturing growth slowed more than expected.