GAZA (Reuters) - Three Palestinian fishermen were killed on Sunday when their boat exploded off the Gaza Strip, a blast that a human rights group said was likely caused by errant Palestinian rocket fire. The Palestinian Center for Human Rights said the boat was two miles offshore when the shell hit and “completely destroyed it”. “The center condemns the incident, which indications suggest mostly likely occurred as a result of resistance training,” said the statement, referring to Palestinian militant groups. Israel’s military denied any connection to the incident and said “our indications show that their deaths were caused by an explosion inside Gaza”. The Interior Ministry in Gaza, which is run by the Islamist group Hamas, said it was investigating the incident. Hamas’ armed wing said it opened an investigation into the “painful incident” and would publish the results as soon as possible.