At least five people have been reportedly killed and more than forty wounded in sectarian violence in Pakistan\'s northern valley of Gilgit. Gunmen opened fire during a strike in a northern Pakistani city popular with tourists, officials said. Sunni Islamists called the strike in Gilgit over the arrest of one of their leaders for his alleged involvement in a sectarian attack on a funeral in February that left 18 dead. \"The unknown gunmen opened fire on a group of Sunnis while they were appealing to people to shut their shops in response to the strike call,\" senior local police official Ali Sher told AFP. Officers were investigating reports of a hand grenade attack. A curfew was imposed in the city after the incident to bring the situation under control, he said. In the February incident, gunmen disguised in military fatigues hauled 18 Shiite Muslim men off buses and shot them dead in cold blood in the northern district of Kohistan, which neighbours the Swat valley, a former Taliban stronghold. A local intelligence official, who did not want to be identified, confirmed Tuesday\'s death toll and also said a hand grenade had been used. \"But we still don\'t know who the attackers were,\" he said. \"What we can say at the moment is that tensions have been mounting high between Shiite and Sunni population in the area for the last many weeks.\" Gilgit is the capital of Pakistan\'s far northern Gilgit-Baltistan region and is popular with mountaineers as a gateway to the Karakoram and Himalayan mountain ranges. Human rights groups have heavily criticised the Pakistani government for failing to crack down on sectarian violence between the country\'s majority Sunni and minority Shiite Muslim communities that has killed thousands.