The sound of gun shots and explosions echoed through the centre of Srinagar after gunmen opened fire in Lal Chowk, the main square in the city's commercial district. After a relatively quiet period in Kashmir, there have been several recent attacks - four soldiers were killed in an ambush by militants last week. But this latest attack is even more audacious, right in the heart of one of the most heavily policed cities in the world. Violent separatist groups, some of them backed by Pakistan, have taken up arms against Indian rule in Kashmir for 20 years. The fighting is far less intense than it was in the 1990s, but a political solution to Kashmir's problems remains elusive. So it's been a bloody start to the New Year in this highly sensitive region, which has been divided between India and Pakistan for decades. In another sign of the complexity of the conflict, four Pakistani soldiers have been killed by a suicide bomber in Pakistan-administered Kashmir. It's a worrying development for the Pakistani authorities, which suggests that Taliban militants may be trying to expand their area of operations.