AHMEDABAD, India, Aug 3 (Reuters) - At least 10 people were killed and 35 injured on Sunday when a gas cylinder explosion brought down three residential buildings in western India, police said. Several others were feared trapped under the debris of the flattened buildings in Surat, which accounts for 90 percent of India's diamond exports worth $8 billion a year. "The toll could rise as and when the rubble is cleared," G.A Shaikh, a senior police official, told Reuters by telephone from Surat, which is 250 km (156 miles) south of Ahmedabad, the state's main city. Police said a diamond...