(Updates with previous attacks) SRINAGAR, India, July 31 (Reuters) - Six people, including a top Indian army officer, were killed in a gunbattle between troops and militants trying to sneak into Indian Kashmir from the Pakistani side on Tuesday, an army spokesman said. The Indian colonel was the most senior officer to be killed this year in the revolt-torn Himalayan region, which has seen a spurt in separatist violence with the onset of summer. "A fierce encounter broke out after the army challenged a group of infiltrators this morning in Uri sector," said spokesman Lieutenant-Colonel A.K. Mathur. "A colonel and a soldier lost their lives." Mathur said four militants were also killed in the clash which was still continuing in the Uri area, about 100 km (60 miles) west of Srinagar, Indian Kashmir's summer capital. Militants continue to sneak across the frontline despite a fence along the militarised Line of Control which divides Kashmir between India and Pakistan. Mathur said this was the second major infiltration attempt by militants in the last two weeks. 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. Police blamed militants on Tuesday for two attacks on vehicles carrying Indian tourists in the last two days, killing a total of eight people and injuring 27 others. A teenage boy and his younger brother were killed and six others were wounded when militants threw an explosive device at a car carrying tourists in southern Kashmir on Monday evening, a police statement said. On Sunday, six people were killed and at least 21 wounded by when a grenade was lobbed at a tourist coach in Srinagar, said police, adding that Lashkar-e-Taiba, a Pakistan-based militant group, was responsible for the attack.