(Updates death toll, new details in paragraphs 3-4, 6-8) SRINAGAR, India, July 29 (Reuters) - Six people, including four women, were killed and at least 21 wounded on Sunday by an explosion aboard a tourist coach in Kashmir's main city, police and witnesses said. Police were unsure if it was a grenade attack by militants or if a faulty air-conditioner had exploded inside the coach. "A low intensity blast took place in a tourist bus, killing six persons," a police statement said, adding that the cause of the explosion blast was under investigation. A senior police officer said an attack by militants was not ruled out. Police said four of the dead and all the injured were Muslim holidaymakers from the western state of Gujarat. "We were returning after a prayer at Hazratbal and there was a sudden bang," Imtiyaz Mustufa, an injured tourist, told Reuters, referring to Kashmir's holiest shrine which houses what some believe is a hair from the beard of the Prophet Mohammad. "Then there were glass and metal pieces around me. People were crying and writhing in blood." No militant group has claimed responsibility for the explosion near Shalimar Garden, a popular tourist spot in Srinagar, the summer capital of the troubled Himalayan region. The explosion comes a day after India's Defence Minister A.K. Antony said the security situation was "fast improving" in Kashmir. At least a dozen Indian tourists were killed and scores wounded in attacks on their vehicles by suspected separatist militants last year. Officials say more than 42,000 people have been killed in Kashmir since a revolt against Indian rule erupted in 1989. But human rights groups put the toll at about 60,000.
