SRINAGAR, India, Jan 22 (Reuters) - Separatist militants threw a grenade at a police patrol in Indian Kashmir on Monday, wounding 13 people at a nearby bus stand, police said. Security has been stepped up in Kashmir and other parts of India ahead of Republic Day, which falls on Jan. 26 and marks the day in 1950 the country adopted its republican constitution. Militant groups in Jammu and Kashmir -- mainly Hindu India's only Muslim-majority state -- and guerrilla outfits in other Indian states often time attacks on and around the holiday to highlight their causes. The attack took place in the town of Pattan, 27 km (15 miles) north of Srinagar, the region's main city. "Two of the 13 are in a serious condition," Shameem Ahmad, a police official, said. "The explosion created panic." No militant group has claimed responsibility. Officials say more than 40,000 people have been killed in Kashmir in the 17-year Muslim separatist revolt against Indian rule. Human rights groups put the toll at around 60,000 dead or missing.