A Hamas gunman opened fire at a Palestinian policeman on Saturday, moderately wounding the officer in the shoulder, officials said. The shooting threatened to raise tensions between the Islamic group and the Palestinian Authority, and comes just a month before Hamas and the ruling Fatah Party compete in parliamentary elections. Officials said the policeman stopped a group of armed Hamas members at a routine checkpoint in Gaza City, and the gunmen opened fire and fled. The Palestinian Interior Ministry said security forces would beat "with an iron fist all those who shed Palestinian blood and assault Palestinian security personnel." There was no immediate comment from Hamas.