By Joe Brock ABUJA (Reuters) - Nigerian authorities have largely ignored sectarian clashes in the nation's religiously mixed central region that have killed 3,000 people since 2010, Human Rights Watch said on Thursday. Local police rejected the findings by the international watchdog, which said that a series of massacres and tit-for-tat sectarian attacks have gone largely unpunished as police overlooked witnesses or failed to collect evidence properly. "Witnesses came forward to tell their stories, compiled lists of the dead, and identified the attackers, but in most cases nothing was done," said Daniel Bekele, Africa director at Human Rights Watch. The report was based on interviews with 180 witnesses and victims in Kaduna and Plateau states, which lie in Nigeria's volatile "Middle Belt", where the largely Christian south meets the mostly Muslim north.